

try:
    from argparse import *
except ImportError: 
    # below here is argparse v1.2.1 from PyPI
    # Author: Steven J. Bethard <steven.bethard@gmail.com>.

    """Command-line parsing library

    This module is an optparse-inspired command-line parsing library that:

        - handles both optional and positional arguments
        - produces highly informative usage messages
        - supports parsers that dispatch to sub-parsers

    The following is a simple usage example that sums integers from the
    command-line and writes the result to a file::

        parser = argparse.ArgumentParser(
            description='sum the integers at the command line')
        parser.add_argument(
            'integers', metavar='int', nargs='+', type=int,
            help='an integer to be summed')
        parser.add_argument(
            '--log', default=sys.stdout, type=argparse.FileType('w'),
            help='the file where the sum should be written')
        args = parser.parse_args()
        args.log.write('%s' % sum(args.integers))
        args.log.close()

    The module contains the following public classes:

        - ArgumentParser -- The main entry point for command-line parsing. As the
            example above shows, the add_argument() method is used to populate
            the parser with actions for optional and positional arguments. Then
            the parse_args() method is invoked to convert the args at the
            command-line into an object with attributes.

        - ArgumentError -- The exception raised by ArgumentParser objects when
            there are errors with the parser's actions. Errors raised while
            parsing the command-line are caught by ArgumentParser and emitted
            as command-line messages.

        - FileType -- A factory for defining types of files to be created. As the
            example above shows, instances of FileType are typically passed as
            the type= argument of add_argument() calls.

        - Action -- The base class for parser actions. Typically actions are
            selected by passing strings like 'store_true' or 'append_const' to
            the action= argument of add_argument(). However, for greater
            customization of ArgumentParser actions, subclasses of Action may
            be defined and passed as the action= argument.

        - HelpFormatter, RawDescriptionHelpFormatter, RawTextHelpFormatter,
            ArgumentDefaultsHelpFormatter -- Formatter classes which
            may be passed as the formatter_class= argument to the
            ArgumentParser constructor. HelpFormatter is the default,
            RawDescriptionHelpFormatter and RawTextHelpFormatter tell the parser
            not to change the formatting for help text, and
            ArgumentDefaultsHelpFormatter adds information about argument defaults
            to the help.

    All other classes in this module are considered implementation details.
    (Also note that HelpFormatter and RawDescriptionHelpFormatter are only
    considered public as object names -- the API of the formatter objects is
    still considered an implementation detail.)
    """

    __version__ = '1.2.1'
    __all__ = [
        'ArgumentParser',
        'ArgumentError',
        'ArgumentTypeError',
        'FileType',
        'HelpFormatter',
        'ArgumentDefaultsHelpFormatter',
        'RawDescriptionHelpFormatter',
        'RawTextHelpFormatter',
        'Namespace',
        'Action',
        'ONE_OR_MORE',
        'OPTIONAL',
        'PARSER',
        'REMAINDER',
        'SUPPRESS',
        'ZERO_OR_MORE',
    ]


    import copy as _copy
    import os as _os
    import re as _re
    import sys as _sys
    import textwrap as _textwrap

    from gettext import gettext as _

    try:
        set
    except NameError:
        # for python < 2.4 compatibility (sets module is there since 2.3):
        from sets import Set as set

    try:
        str
    except NameError:
        str = str

    try:
        sorted
    except NameError:
        # for python < 2.4 compatibility:
        def sorted(iterable, reverse=False):
            result = list(iterable)
            result.sort()
            if reverse:
                result.reverse()
            return result


    def _callable(obj):
        return hasattr(obj, '__call__') or hasattr(obj, '__bases__')


    SUPPRESS = '==SUPPRESS=='

    OPTIONAL = '?'
    ZERO_OR_MORE = '*'
    ONE_OR_MORE = '+'
    PARSER = 'A...'
    REMAINDER = '...'
    _UNRECOGNIZED_ARGS_ATTR = '_unrecognized_args'

    # =============================
    # Utility functions and classes
    # =============================

    class _AttributeHolder(object):
        """Abstract base class that provides __repr__.

        The __repr__ method returns a string in the format::
            ClassName(attr=name, attr=name, ...)
        The attributes are determined either by a class-level attribute,
        '_kwarg_names', or by inspecting the instance __dict__.
        """

        def __repr__(self):
            type_name = type(self).__name__
            arg_strings = []
            for arg in self._get_args():
                arg_strings.append(repr(arg))
            for name, value in self._get_kwargs():
                arg_strings.append('%s=%r' % (name, value))
            return '%s(%s)' % (type_name, ', '.join(arg_strings))

        def _get_kwargs(self):
            return sorted(self.__dict__.items())

        def _get_args(self):
            return []


    def _ensure_value(namespace, name, value):
        if getattr(namespace, name, None) is None:
            setattr(namespace, name, value)
        return getattr(namespace, name)


    # ===============
    # Formatting Help
    # ===============

    class HelpFormatter(object):
        """Formatter for generating usage messages and argument help strings.

        Only the name of this class is considered a public API. All the methods
        provided by the class are considered an implementation detail.
        """

        def __init__(self,
                     prog,
                     indent_increment=2,
                     max_help_position=24,
                     width=None):

            # default setting for width
            if width is None:
                try:
                    width = int(_os.environ['COLUMNS'])
                except (KeyError, ValueError):
                    width = 80
                width -= 2

            self._prog = prog
            self._indent_increment = indent_increment
            self._max_help_position = max_help_position
            self._width = width

            self._current_indent = 0
            self._level = 0
            self._action_max_length = 0

            self._root_section = self._Section(self, None)
            self._current_section = self._root_section

            self._whitespace_matcher = _re.compile(r'\s+')
            self._long_break_matcher = _re.compile(r'\n\n\n+')

        # ===============================
        # Section and indentation methods
        # ===============================
        def _indent(self):
            self._current_indent += self._indent_increment
            self._level += 1

        def _dedent(self):
            self._current_indent -= self._indent_increment
            assert self._current_indent >= 0, 'Indent decreased below 0.'
            self._level -= 1

        class _Section(object):

            def __init__(self, formatter, parent, heading=None):
                self.formatter = formatter
                self.parent = parent
                self.heading = heading
                self.items = []

            def format_help(self):
                # format the indented section
                if self.parent is not None:
                    self.formatter._indent()
                join = self.formatter._join_parts
                for func, args in self.items:
                    func(*args)
                item_help = join([func(*args) for func, args in self.items])
                if self.parent is not None:
                    self.formatter._dedent()

                # return nothing if the section was empty
                if not item_help:
                    return ''

                # add the heading if the section was non-empty
                if self.heading is not SUPPRESS and self.heading is not None:
                    current_indent = self.formatter._current_indent
                    heading = '%*s%s:\n' % (current_indent, '', self.heading)
                else:
                    heading = ''

                # join the section-initial newline, the heading and the help
                return join(['\n', heading, item_help, '\n'])

        def _add_item(self, func, args):
            self._current_section.items.append((func, args))

        # ========================
        # Message building methods
        # ========================
        def start_section(self, heading):
            self._indent()
            section = self._Section(self, self._current_section, heading)
            self._add_item(section.format_help, [])
            self._current_section = section

        def end_section(self):
            self._current_section = self._current_section.parent
            self._dedent()

        def add_text(self, text):
            if text is not SUPPRESS and text is not None:
                self._add_item(self._format_text, [text])

        def add_usage(self, usage, actions, groups, prefix=None):
            if usage is not SUPPRESS:
                args = usage, actions, groups, prefix
                self._add_item(self._format_usage, args)

        def add_argument(self, action):
            if action.help is not SUPPRESS:

                # find all invocations
                get_invocation = self._format_action_invocation
                invocations = [get_invocation(action)]
                for subaction in self._iter_indented_subactions(action):
                    invocations.append(get_invocation(subaction))

                # update the maximum item length
                invocation_length = max([len(s) for s in invocations])
                action_length = invocation_length + self._current_indent
                self._action_max_length = max(self._action_max_length,
                                              action_length)

                # add the item to the list
                self._add_item(self._format_action, [action])

        def add_arguments(self, actions):
            for action in actions:
                self.add_argument(action)

        # =======================
        # Help-formatting methods
        # =======================
        def format_help(self):
            help = self._root_section.format_help()
            if help:
                help = self._long_break_matcher.sub('\n\n', help)
                help = help.strip('\n') + '\n'
            return help

        def _join_parts(self, part_strings):
            return ''.join([part
                            for part in part_strings
                            if part and part is not SUPPRESS])

        def _format_usage(self, usage, actions, groups, prefix):
            if prefix is None:
                prefix = _('usage: ')

            # if usage is specified, use that
            if usage is not None:
                usage = usage % dict(prog=self._prog)

            # if no optionals or positionals are available, usage is just prog
            elif usage is None and not actions:
                usage = '%(prog)s' % dict(prog=self._prog)

            # if optionals and positionals are available, calculate usage
            elif usage is None:
                prog = '%(prog)s' % dict(prog=self._prog)

                # split optionals from positionals
                optionals = []
                positionals = []
                for action in actions:
                    if action.option_strings:
                        optionals.append(action)
                    else:
                        positionals.append(action)

                # build full usage string
                format = self._format_actions_usage
                action_usage = format(optionals + positionals, groups)
                usage = ' '.join([s for s in [prog, action_usage] if s])

                # wrap the usage parts if it's too long
                text_width = self._width - self._current_indent
                if len(prefix) + len(usage) > text_width:

                    # break usage into wrappable parts
                    part_regexp = r'\(.*?\)+|\[.*?\]+|\S+'
                    opt_usage = format(optionals, groups)
                    pos_usage = format(positionals, groups)
                    opt_parts = _re.findall(part_regexp, opt_usage)
                    pos_parts = _re.findall(part_regexp, pos_usage)
                    assert ' '.join(opt_parts) == opt_usage
                    assert ' '.join(pos_parts) == pos_usage

                    # helper for wrapping lines
                    def get_lines(parts, indent, prefix=None):
                        lines = []
                        line = []
                        if prefix is not None:
                            line_len = len(prefix) - 1
                        else:
                            line_len = len(indent) - 1
                        for part in parts:
                            if line_len + 1 + len(part) > text_width:
                                lines.append(indent + ' '.join(line))
                                line = []
                                line_len = len(indent) - 1
                            line.append(part)
                            line_len += len(part) + 1
                        if line:
                            lines.append(indent + ' '.join(line))
                        if prefix is not None:
                            lines[0] = lines[0][len(indent):]
                        return lines

                    # if prog is short, follow it with optionals or positionals
                    if len(prefix) + len(prog) <= 0.75 * text_width:
                        indent = ' ' * (len(prefix) + len(prog) + 1)
                        if opt_parts:
                            lines = get_lines([prog] + opt_parts, indent, prefix)
                            lines.extend(get_lines(pos_parts, indent))
                        elif pos_parts:
                            lines = get_lines([prog] + pos_parts, indent, prefix)
                        else:
                            lines = [prog]

                    # if prog is long, put it on its own line
                    else:
                        indent = ' ' * len(prefix)
                        parts = opt_parts + pos_parts
                        lines = get_lines(parts, indent)
                        if len(lines) > 1:
                            lines = []
                            lines.extend(get_lines(opt_parts, indent))
                            lines.extend(get_lines(pos_parts, indent))
                        lines = [prog] + lines

                    # join lines into usage
                    usage = '\n'.join(lines)

            # prefix with 'usage:'
            return '%s%s\n\n' % (prefix, usage)

        def _format_actions_usage(self, actions, groups):
            # find group indices and identify actions in groups
            group_actions = set()
            inserts = {}
            for group in groups:
                try:
                    start = actions.index(group._group_actions[0])
                except ValueError:
                    continue
                else:
                    end = start + len(group._group_actions)
                    if actions[start:end] == group._group_actions:
                        for action in group._group_actions:
                            group_actions.add(action)
                        if not group.required:
                            if start in inserts:
                                inserts[start] += ' ['
                            else:
                                inserts[start] = '['
                            inserts[end] = ']'
                        else:
                            if start in inserts:
                                inserts[start] += ' ('
                            else:
                                inserts[start] = '('
                            inserts[end] = ')'
                        for i in range(start + 1, end):
                            inserts[i] = '|'

            # collect all actions format strings
            parts = []
            for i, action in enumerate(actions):

                # suppressed arguments are marked with None
                # remove | separators for suppressed arguments
                if action.help is SUPPRESS:
                    parts.append(None)
                    if inserts.get(i) == '|':
                        inserts.pop(i)
                    elif inserts.get(i + 1) == '|':
                        inserts.pop(i + 1)

                # produce all arg strings
                elif not action.option_strings:
                    part = self._format_args(action, action.dest)

                    # if it's in a group, strip the outer []
                    if action in group_actions:
                        if part[0] == '[' and part[-1] == ']':
                            part = part[1:-1]

                    # add the action string to the list
                    parts.append(part)

                # produce the first way to invoke the option in brackets
                else:
                    option_string = action.option_strings[0]

                    # if the Optional doesn't take a value, format is:
                    #    -s or --long
                    if action.nargs == 0:
                        part = '%s' % option_string

                    # if the Optional takes a value, format is:
                    #    -s ARGS or --long ARGS
                    else:
                        default = action.dest.upper()
                        args_string = self._format_args(action, default)
                        part = '%s %s' % (option_string, args_string)

                    # make it look optional if it's not required or in a group
                    if not action.required and action not in group_actions:
                        part = '[%s]' % part

                    # add the action string to the list
                    parts.append(part)

            # insert things at the necessary indices
            for i in sorted(inserts, reverse=True):
                parts[i:i] = [inserts[i]]

            # join all the action items with spaces
            text = ' '.join([item for item in parts if item is not None])

            # clean up separators for mutually exclusive groups
            open = r'[\[(]'
            close = r'[\])]'
            text = _re.sub(r'(%s) ' % open, r'\1', text)
            text = _re.sub(r' (%s)' % close, r'\1', text)
            text = _re.sub(r'%s *%s' % (open, close), r'', text)
            text = _re.sub(r'\(([^|]*)\)', r'\1', text)
            text = text.strip()

            # return the text
            return text

        def _format_text(self, text):
            if '%(prog)' in text:
                text = text % dict(prog=self._prog)
            text_width = self._width - self._current_indent
            indent = ' ' * self._current_indent
            return self._fill_text(text, text_width, indent) + '\n\n'

        def _format_action(self, action):
            # determine the required width and the entry label
            help_position = min(self._action_max_length + 2,
                                self._max_help_position)
            help_width = self._width - help_position
            action_width = help_position - self._current_indent - 2
            action_header = self._format_action_invocation(action)

            # ho nelp; start on same line and add a final newline
            if not action.help:
                tup = self._current_indent, '', action_header
                action_header = '%*s%s\n' % tup

            # short action name; start on the same line and pad two spaces
            elif len(action_header) <= action_width:
                tup = self._current_indent, '', action_width, action_header
                action_header = '%*s%-*s  ' % tup
                indent_first = 0

            # long action name; start on the next line
            else:
                tup = self._current_indent, '', action_header
                action_header = '%*s%s\n' % tup
                indent_first = help_position

            # collect the pieces of the action help
            parts = [action_header]

            # if there was help for the action, add lines of help text
            if action.help:
                help_text = self._expand_help(action)
                help_lines = self._split_lines(help_text, help_width)
                parts.append('%*s%s\n' % (indent_first, '', help_lines[0]))
                for line in help_lines[1:]:
                    parts.append('%*s%s\n' % (help_position, '', line))

            # or add a newline if the description doesn't end with one
            elif not action_header.endswith('\n'):
                parts.append('\n')

            # if there are any sub-actions, add their help as well
            for subaction in self._iter_indented_subactions(action):
                parts.append(self._format_action(subaction))

            # return a single string
            return self._join_parts(parts)

        def _format_action_invocation(self, action):
            if not action.option_strings:
                metavar, = self._metavar_formatter(action, action.dest)(1)
                return metavar

            else:
                parts = []

                # if the Optional doesn't take a value, format is:
                #    -s, --long
                if action.nargs == 0:
                    parts.extend(action.option_strings)

                # if the Optional takes a value, format is:
                #    -s ARGS, --long ARGS
                else:
                    default = action.dest.upper()
                    args_string = self._format_args(action, default)
                    for option_string in action.option_strings:
                        parts.append('%s %s' % (option_string, args_string))

                return ', '.join(parts)

        def _metavar_formatter(self, action, default_metavar):
            if action.metavar is not None:
                result = action.metavar
            elif action.choices is not None:
                choice_strs = [str(choice) for choice in action.choices]
                result = '{%s}' % ','.join(choice_strs)
            else:
                result = default_metavar

            def format(tuple_size):
                if isinstance(result, tuple):
                    return result
                else:
                    return (result, ) * tuple_size
            return format

        def _format_args(self, action, default_metavar):
            get_metavar = self._metavar_formatter(action, default_metavar)
            if action.nargs is None:
                result = '%s' % get_metavar(1)
            elif action.nargs == OPTIONAL:
                result = '[%s]' % get_metavar(1)
            elif action.nargs == ZERO_OR_MORE:
                result = '[%s [%s ...]]' % get_metavar(2)
            elif action.nargs == ONE_OR_MORE:
                result = '%s [%s ...]' % get_metavar(2)
            elif action.nargs == REMAINDER:
                result = '...'
            elif action.nargs == PARSER:
                result = '%s ...' % get_metavar(1)
            else:
                formats = ['%s' for _ in range(action.nargs)]
                result = ' '.join(formats) % get_metavar(action.nargs)
            return result

        def _expand_help(self, action):
            params = dict(vars(action), prog=self._prog)
            for name in list(params):
                if params[name] is SUPPRESS:
                    del params[name]
            for name in list(params):
                if hasattr(params[name], '__name__'):
                    params[name] = params[name].__name__
            if params.get('choices') is not None:
                choices_str = ', '.join([str(c) for c in params['choices']])
                params['choices'] = choices_str
            return self._get_help_string(action) % params

        def _iter_indented_subactions(self, action):
            try:
                get_subactions = action._get_subactions
            except AttributeError:
                pass
            else:
                self._indent()
                for subaction in get_subactions():
                    yield subaction
                self._dedent()

        def _split_lines(self, text, width):
            text = self._whitespace_matcher.sub(' ', text).strip()
            return _textwrap.wrap(text, width)

        def _fill_text(self, text, width, indent):
            text = self._whitespace_matcher.sub(' ', text).strip()
            return _textwrap.fill(text, width, initial_indent=indent,
                                               subsequent_indent=indent)

        def _get_help_string(self, action):
            return action.help


    class RawDescriptionHelpFormatter(HelpFormatter):
        """Help message formatter which retains any formatting in descriptions.

        Only the name of this class is considered a public API. All the methods
        provided by the class are considered an implementation detail.
        """

        def _fill_text(self, text, width, indent):
            return ''.join([indent + line for line in text.splitlines(True)])


    class RawTextHelpFormatter(RawDescriptionHelpFormatter):
        """Help message formatter which retains formatting of all help text.

        Only the name of this class is considered a public API. All the methods
        provided by the class are considered an implementation detail.
        """

        def _split_lines(self, text, width):
            return text.splitlines()


    class ArgumentDefaultsHelpFormatter(HelpFormatter):
        """Help message formatter which adds default values to argument help.

        Only the name of this class is considered a public API. All the methods
        provided by the class are considered an implementation detail.
        """

        def _get_help_string(self, action):
            help = action.help
            if '%(default)' not in action.help:
                if action.default is not SUPPRESS:
                    defaulting_nargs = [OPTIONAL, ZERO_OR_MORE]
                    if action.option_strings or action.nargs in defaulting_nargs:
                        help += ' (default: %(default)s)'
            return help


    # =====================
    # Options and Arguments
    # =====================

    def _get_action_name(argument):
        if argument is None:
            return None
        elif argument.option_strings:
            return  '/'.join(argument.option_strings)
        elif argument.metavar not in (None, SUPPRESS):
            return argument.metavar
        elif argument.dest not in (None, SUPPRESS):
            return argument.dest
        else:
            return None


    class ArgumentError(Exception):
        """An error from creating or using an argument (optional or positional).

        The string value of this exception is the message, augmented with
        information about the argument that caused it.
        """

        def __init__(self, argument, message):
            self.argument_name = _get_action_name(argument)
            self.message = message

        def __str__(self):
            if self.argument_name is None:
                format = '%(message)s'
            else:
                format = 'argument %(argument_name)s: %(message)s'
            return format % dict(message=self.message,
                                 argument_name=self.argument_name)


    class ArgumentTypeError(Exception):
        """An error from trying to convert a command line string to a type."""
        pass


    # ==============
    # Action classes
    # ==============

    class Action(_AttributeHolder):
        """Information about how to convert command line strings to Python objects.

        Action objects are used by an ArgumentParser to represent the information
        needed to parse a single argument from one or more strings from the
        command line. The keyword arguments to the Action constructor are also
        all attributes of Action instances.

        Keyword Arguments:

            - option_strings -- A list of command-line option strings which
                should be associated with this action.

            - dest -- The name of the attribute to hold the created object(s)

            - nargs -- The number of command-line arguments that should be
                consumed. By default, one argument will be consumed and a single
                value will be produced.  Other values include:
                    - N (an integer) consumes N arguments (and produces a list)
                    - '?' consumes zero or one arguments
                    - '*' consumes zero or more arguments (and produces a list)
                    - '+' consumes one or more arguments (and produces a list)
                Note that the difference between the default and nargs=1 is that
                with the default, a single value will be produced, while with
                nargs=1, a list containing a single value will be produced.

            - const -- The value to be produced if the option is specified and the
                option uses an action that takes no values.

            - default -- The value to be produced if the option is not specified.

            - type -- The type which the command-line arguments should be converted
                to, should be one of 'string', 'int', 'float', 'complex' or a
                callable object that accepts a single string argument. If None,
                'string' is assumed.

            - choices -- A container of values that should be allowed. If not None,
                after a command-line argument has been converted to the appropriate
                type, an exception will be raised if it is not a member of this
                collection.

            - required -- True if the action must always be specified at the
                command line. This is only meaningful for optional command-line
                arguments.

            - help -- The help string describing the argument.

            - metavar -- The name to be used for the option's argument with the
                help string. If None, the 'dest' value will be used as the name.
        """

        def __init__(self,
                     option_strings,
                     dest,
                     nargs=None,
                     const=None,
                     default=None,
                     type=None,
                     choices=None,
                     required=False,
                     help=None,
                     metavar=None):
            self.option_strings = option_strings
            self.dest = dest
            self.nargs = nargs
            self.const = const
            self.default = default
            self.type = type
            self.choices = choices
            self.required = required
            self.help = help
            self.metavar = metavar

        def _get_kwargs(self):
            names = [
                'option_strings',
                'dest',
                'nargs',
                'const',
                'default',
                'type',
                'choices',
                'help',
                'metavar',
            ]
            return [(name, getattr(self, name)) for name in names]

        def __call__(self, parser, namespace, values, option_string=None):
            raise NotImplementedError(_('.__call__() not defined'))


    class _StoreAction(Action):

        def __init__(self,
                     option_strings,
                     dest,
                     nargs=None,
                     const=None,
                     default=None,
                     type=None,
                     choices=None,
                     required=False,
                     help=None,
                     metavar=None):
            if nargs == 0:
                raise ValueError('nargs for store actions must be > 0; if you '
                                 'have nothing to store, actions such as store '
                                 'true or store const may be more appropriate')
            if const is not None and nargs != OPTIONAL:
                raise ValueError('nargs must be %r to supply const' % OPTIONAL)
            super(_StoreAction, self).__init__(
                option_strings=option_strings,
                dest=dest,
                nargs=nargs,
                const=const,
                default=default,
                type=type,
                choices=choices,
                required=required,
                help=help,
                metavar=metavar)

        def __call__(self, parser, namespace, values, option_string=None):
            setattr(namespace, self.dest, values)


    class _StoreConstAction(Action):

        def __init__(self,
                     option_strings,
                     dest,
                     const,
                     default=None,
                     required=False,
                     help=None,
                     metavar=None):
            super(_StoreConstAction, self).__init__(
                option_strings=option_strings,
                dest=dest,
                nargs=0,
                const=const,
                default=default,
                required=required,
                help=help)

        def __call__(self, parser, namespace, values, option_string=None):
            setattr(namespace, self.dest, self.const)


    class _StoreTrueAction(_StoreConstAction):

        def __init__(self,
                     option_strings,
                     dest,
                     default=False,
                     required=False,
                     help=None):
            super(_StoreTrueAction, self).__init__(
                option_strings=option_strings,
                dest=dest,
                const=True,
                default=default,
                required=required,
                help=help)


    class _StoreFalseAction(_StoreConstAction):

        def __init__(self,
                     option_strings,
                     dest,
                     default=True,
                     required=False,
                     help=None):
            super(_StoreFalseAction, self).__init__(
                option_strings=option_strings,
                dest=dest,
                const=False,
                default=default,
                required=required,
                help=help)


    class _AppendAction(Action):

        def __init__(self,
                     option_strings,
                     dest,
                     nargs=None,
                     const=None,
                     default=None,
                     type=None,
                     choices=None,
                     required=False,
                     help=None,
                     metavar=None):
            if nargs == 0:
                raise ValueError('nargs for append actions must be > 0; if arg '
                                 'strings are not supplying the value to append, '
                                 'the append const action may be more appropriate')
            if const is not None and nargs != OPTIONAL:
                raise ValueError('nargs must be %r to supply const' % OPTIONAL)
            super(_AppendAction, self).__init__(
                option_strings=option_strings,
                dest=dest,
                nargs=nargs,
                const=const,
                default=default,
                type=type,
                choices=choices,
                required=required,
                help=help,
                metavar=metavar)

        def __call__(self, parser, namespace, values, option_string=None):
            items = _copy.copy(_ensure_value(namespace, self.dest, []))
            items.append(values)
            setattr(namespace, self.dest, items)


    class _AppendConstAction(Action):

        def __init__(self,
                     option_strings,
                     dest,
                     const,
                     default=None,
                     required=False,
                     help=None,
                     metavar=None):
            super(_AppendConstAction, self).__init__(
                option_strings=option_strings,
                dest=dest,
                nargs=0,
                const=const,
                default=default,
                required=required,
                help=help,
                metavar=metavar)

        def __call__(self, parser, namespace, values, option_string=None):
            items = _copy.copy(_ensure_value(namespace, self.dest, []))
            items.append(self.const)
            setattr(namespace, self.dest, items)


    class _CountAction(Action):

        def __init__(self,
                     option_strings,
                     dest,
                     default=None,
                     required=False,
                     help=None):
            super(_CountAction, self).__init__(
                option_strings=option_strings,
                dest=dest,
                nargs=0,
                default=default,
                required=required,
                help=help)

        def __call__(self, parser, namespace, values, option_string=None):
            new_count = _ensure_value(namespace, self.dest, 0) + 1
            setattr(namespace, self.dest, new_count)


    class _HelpAction(Action):

        def __init__(self,
                     option_strings,
                     dest=SUPPRESS,
                     default=SUPPRESS,
                     help=None):
            super(_HelpAction, self).__init__(
                option_strings=option_strings,
                dest=dest,
                default=default,
                nargs=0,
                help=help)

        def __call__(self, parser, namespace, values, option_string=None):
            parser.print_help()
            parser.exit()


    class _VersionAction(Action):

        def __init__(self,
                     option_strings,
                     version=None,
                     dest=SUPPRESS,
                     default=SUPPRESS,
                     help="show program's version number and exit"):
            super(_VersionAction, self).__init__(
                option_strings=option_strings,
                dest=dest,
                default=default,
                nargs=0,
                help=help)
            self.version = version

        def __call__(self, parser, namespace, values, option_string=None):
            version = self.version
            if version is None:
                version = parser.version
            formatter = parser._get_formatter()
            formatter.add_text(version)
            parser.exit(message=formatter.format_help())


    class _SubParsersAction(Action):

        class _ChoicesPseudoAction(Action):

            def __init__(self, name, help):
                sup = super(_SubParsersAction._ChoicesPseudoAction, self)
                sup.__init__(option_strings=[], dest=name, help=help)

        def __init__(self,
                     option_strings,
                     prog,
                     parser_class,
                     dest=SUPPRESS,
                     help=None,
                     metavar=None):

            self._prog_prefix = prog
            self._parser_class = parser_class
            self._name_parser_map = {}
            self._choices_actions = []

            super(_SubParsersAction, self).__init__(
                option_strings=option_strings,
                dest=dest,
                nargs=PARSER,
                choices=self._name_parser_map,
                help=help,
                metavar=metavar)

        def add_parser(self, name, **kwargs):
            # set prog from the existing prefix
            if kwargs.get('prog') is None:
                kwargs['prog'] = '%s %s' % (self._prog_prefix, name)

            # create a pseudo-action to hold the choice help
            if 'help' in kwargs:
                help = kwargs.pop('help')
                choice_action = self._ChoicesPseudoAction(name, help)
                self._choices_actions.append(choice_action)

            # create the parser and add it to the map
            parser = self._parser_class(**kwargs)
            self._name_parser_map[name] = parser
            return parser

        def _get_subactions(self):
            return self._choices_actions

        def __call__(self, parser, namespace, values, option_string=None):
            parser_name = values[0]
            arg_strings = values[1:]

            # set the parser name if requested
            if self.dest is not SUPPRESS:
                setattr(namespace, self.dest, parser_name)

            # select the parser
            try:
                parser = self._name_parser_map[parser_name]
            except KeyError:
                tup = parser_name, ', '.join(self._name_parser_map)
                msg = _('unknown parser %r (choices: %s)' % tup)
                raise ArgumentError(self, msg)

            # parse all the remaining options into the namespace
            # store any unrecognized options on the object, so that the top
            # level parser can decide what to do with them
            namespace, arg_strings = parser.parse_known_args(arg_strings, namespace)
            if arg_strings:
                vars(namespace).setdefault(_UNRECOGNIZED_ARGS_ATTR, [])
                getattr(namespace, _UNRECOGNIZED_ARGS_ATTR).extend(arg_strings)


    # ==============
    # Type classes
    # ==============

    class FileType(object):
        """Factory for creating file object types

        Instances of FileType are typically passed as type= arguments to the
        ArgumentParser add_argument() method.

        Keyword Arguments:
            - mode -- A string indicating how the file is to be opened. Accepts the
                same values as the builtin open() function.
            - bufsize -- The file's desired buffer size. Accepts the same values as
                the builtin open() function.
        """

        def __init__(self, mode='r', bufsize=None):
            self._mode = mode
            self._bufsize = bufsize

        def __call__(self, string):
            # the special argument "-" means sys.std{in,out}
            if string == '-':
                if 'r' in self._mode:
                    return _sys.stdin
                elif 'w' in self._mode:
                    return _sys.stdout
                else:
                    msg = _('argument "-" with mode %r' % self._mode)
                    raise ValueError(msg)

            # all other arguments are used as file names
            if self._bufsize:
                return open(string, self._mode, self._bufsize)
            else:
                return open(string, self._mode)

        def __repr__(self):
            args = [self._mode, self._bufsize]
            args_str = ', '.join([repr(arg) for arg in args if arg is not None])
            return '%s(%s)' % (type(self).__name__, args_str)

    # ===========================
    # Optional and Positional Parsing
    # ===========================

    class Namespace(_AttributeHolder):
        """Simple object for storing attributes.

        Implements equality by attribute names and values, and provides a simple
        string representation.
        """

        def __init__(self, **kwargs):
            for name in kwargs:
                setattr(self, name, kwargs[name])

        __hash__ = None

        def __eq__(self, other):
            return vars(self) == vars(other)

        def __ne__(self, other):
            return not (self == other)

        def __contains__(self, key):
            return key in self.__dict__


    class _ActionsContainer(object):

        def __init__(self,
                     description,
                     prefix_chars,
                     argument_default,
                     conflict_handler):
            super(_ActionsContainer, self).__init__()

            self.description = description
            self.argument_default = argument_default
            self.prefix_chars = prefix_chars
            self.conflict_handler = conflict_handler

            # set up registries
            self._registries = {}

            # register actions
            self.register('action', None, _StoreAction)
            self.register('action', 'store', _StoreAction)
            self.register('action', 'store_const', _StoreConstAction)
            self.register('action', 'store_true', _StoreTrueAction)
            self.register('action', 'store_false', _StoreFalseAction)
            self.register('action', 'append', _AppendAction)
            self.register('action', 'append_const', _AppendConstAction)
            self.register('action', 'count', _CountAction)
            self.register('action', 'help', _HelpAction)
            self.register('action', 'version', _VersionAction)
            self.register('action', 'parsers', _SubParsersAction)

            # raise an exception if the conflict handler is invalid
            self._get_handler()

            # action storage
            self._actions = []
            self._option_string_actions = {}

            # groups
            self._action_groups = []
            self._mutually_exclusive_groups = []

            # defaults storage
            self._defaults = {}

            # determines whether an "option" looks like a negative number
            self._negative_number_matcher = _re.compile(r'^-\d+$|^-\d*\.\d+$')

            # whether or not there are any optionals that look like negative
            # numbers -- uses a list so it can be shared and edited
            self._has_negative_number_optionals = []

        # ====================
        # Registration methods
        # ====================
        def register(self, registry_name, value, object):
            registry = self._registries.setdefault(registry_name, {})
            registry[value] = object

        def _registry_get(self, registry_name, value, default=None):
            return self._registries[registry_name].get(value, default)

        # ==================================
        # Namespace default accessor methods
        # ==================================
        def set_defaults(self, **kwargs):
            self._defaults.update(kwargs)

            # if these defaults match any existing arguments, replace
            # the previous default on the object with the new one
            for action in self._actions:
                if action.dest in kwargs:
                    action.default = kwargs[action.dest]

        def get_default(self, dest):
            for action in self._actions:
                if action.dest == dest and action.default is not None:
                    return action.default
            return self._defaults.get(dest, None)


        # =======================
        # Adding argument actions
        # =======================
        def add_argument(self, *args, **kwargs):
            """
            add_argument(dest, ..., name=value, ...)
            add_argument(option_string, option_string, ..., name=value, ...)
            """

            # if no positional args are supplied or only one is supplied and
            # it doesn't look like an option string, parse a positional
            # argument
            chars = self.prefix_chars
            if not args or len(args) == 1 and args[0][0] not in chars:
                if args and 'dest' in kwargs:
                    raise ValueError('dest supplied twice for positional argument')
                kwargs = self._get_positional_kwargs(*args, **kwargs)

            # otherwise, we're adding an optional argument
            else:
                kwargs = self._get_optional_kwargs(*args, **kwargs)

            # if no default was supplied, use the parser-level default
            if 'default' not in kwargs:
                dest = kwargs['dest']
                if dest in self._defaults:
                    kwargs['default'] = self._defaults[dest]
                elif self.argument_default is not None:
                    kwargs['default'] = self.argument_default

            # create the action object, and add it to the parser
            action_class = self._pop_action_class(kwargs)
            if not _callable(action_class):
                raise ValueError('unknown action "%s"' % action_class)
            action = action_class(**kwargs)

            # raise an error if the action type is not callable
            type_func = self._registry_get('type', action.type, action.type)
            if not _callable(type_func):
                raise ValueError('%r is not callable' % type_func)

            return self._add_action(action)

        def add_argument_group(self, *args, **kwargs):
            group = _ArgumentGroup(self, *args, **kwargs)
            self._action_groups.append(group)
            return group

        def add_mutually_exclusive_group(self, **kwargs):
            group = _MutuallyExclusiveGroup(self, **kwargs)
            self._mutually_exclusive_groups.append(group)
            return group

        def _add_action(self, action):
            # resolve any conflicts
            self._check_conflict(action)

            # add to actions list
            self._actions.append(action)
            action.container = self

            # index the action by any option strings it has
            for option_string in action.option_strings:
                self._option_string_actions[option_string] = action

            # set the flag if any option strings look like negative numbers
            for option_string in action.option_strings:
                if self._negative_number_matcher.match(option_string):
                    if not self._has_negative_number_optionals:
                        self._has_negative_number_optionals.append(True)

            # return the created action
            return action

        def _remove_action(self, action):
            self._actions.remove(action)

        def _add_container_actions(self, container):
            # collect groups by titles
            title_group_map = {}
            for group in self._action_groups:
                if group.title in title_group_map:
                    msg = _('cannot merge actions - two groups are named %r')
                    raise ValueError(msg % (group.title))
                title_group_map[group.title] = group

            # map each action to its group
            group_map = {}
            for group in container._action_groups:

                # if a group with the title exists, use that, otherwise
                # create a new group matching the container's group
                if group.title not in title_group_map:
                    title_group_map[group.title] = self.add_argument_group(
                        title=group.title,
                        description=group.description,
                        conflict_handler=group.conflict_handler)

                # map the actions to their new group
                for action in group._group_actions:
                    group_map[action] = title_group_map[group.title]

            # add container's mutually exclusive groups
            # NOTE: if add_mutually_exclusive_group ever gains title= and
            # description= then this code will need to be expanded as above
            for group in container._mutually_exclusive_groups:
                mutex_group = self.add_mutually_exclusive_group(
                    required=group.required)

                # map the actions to their new mutex group
                for action in group._group_actions:
                    group_map[action] = mutex_group

            # add all actions to this container or their group
            for action in container._actions:
                group_map.get(action, self)._add_action(action)

        def _get_positional_kwargs(self, dest, **kwargs):
            # make sure required is not specified
            if 'required' in kwargs:
                msg = _("'required' is an invalid argument for positionals")
                raise TypeError(msg)

            # mark positional arguments as required if at least one is
            # always required
            if kwargs.get('nargs') not in [OPTIONAL, ZERO_OR_MORE]:
                kwargs['required'] = True
            if kwargs.get('nargs') == ZERO_OR_MORE and 'default' not in kwargs:
                kwargs['required'] = True

            # return the keyword arguments with no option strings
            return dict(kwargs, dest=dest, option_strings=[])

        def _get_optional_kwargs(self, *args, **kwargs):
            # determine short and long option strings
            option_strings = []
            long_option_strings = []
            for option_string in args:
                # error on strings that don't start with an appropriate prefix
                if not option_string[0] in self.prefix_chars:
                    msg = _('invalid option string %r: '
                            'must start with a character %r')
                    tup = option_string, self.prefix_chars
                    raise ValueError(msg % tup)

                # strings starting with two prefix characters are long options
                option_strings.append(option_string)
                if option_string[0] in self.prefix_chars:
                    if len(option_string) > 1:
                        if option_string[1] in self.prefix_chars:
                            long_option_strings.append(option_string)

            # infer destination, '--foo-bar' -> 'foo_bar' and '-x' -> 'x'
            dest = kwargs.pop('dest', None)
            if dest is None:
                if long_option_strings:
                    dest_option_string = long_option_strings[0]
                else:
                    dest_option_string = option_strings[0]
                dest = dest_option_string.lstrip(self.prefix_chars)
                if not dest:
                    msg = _('dest= is required for options like %r')
                    raise ValueError(msg % option_string)
                dest = dest.replace('-', '_')

            # return the updated keyword arguments
            return dict(kwargs, dest=dest, option_strings=option_strings)

        def _pop_action_class(self, kwargs, default=None):
            action = kwargs.pop('action', default)
            return self._registry_get('action', action, action)

        def _get_handler(self):
            # determine function from conflict handler string
            handler_func_name = '_handle_conflict_%s' % self.conflict_handler
            try:
                return getattr(self, handler_func_name)
            except AttributeError:
                msg = _('invalid conflict_resolution value: %r')
                raise ValueError(msg % self.conflict_handler)

        def _check_conflict(self, action):

            # find all options that conflict with this option
            confl_optionals = []
            for option_string in action.option_strings:
                if option_string in self._option_string_actions:
                    confl_optional = self._option_string_actions[option_string]
                    confl_optionals.append((option_string, confl_optional))

            # resolve any conflicts
            if confl_optionals:
                conflict_handler = self._get_handler()
                conflict_handler(action, confl_optionals)

        def _handle_conflict_error(self, action, conflicting_actions):
            message = _('conflicting option string(s): %s')
            conflict_string = ', '.join([option_string
                                         for option_string, action
                                         in conflicting_actions])
            raise ArgumentError(action, message % conflict_string)

        def _handle_conflict_resolve(self, action, conflicting_actions):

            # remove all conflicting options
            for option_string, action in conflicting_actions:

                # remove the conflicting option
                action.option_strings.remove(option_string)
                self._option_string_actions.pop(option_string, None)

                # if the option now has no option string, remove it from the
                # container holding it
                if not action.option_strings:
                    action.container._remove_action(action)


    class _ArgumentGroup(_ActionsContainer):

        def __init__(self, container, title=None, description=None, **kwargs):
            # add any missing keyword arguments by checking the container
            update = kwargs.setdefault
            update('conflict_handler', container.conflict_handler)
            update('prefix_chars', container.prefix_chars)
            update('argument_default', container.argument_default)
            super_init = super(_ArgumentGroup, self).__init__
            super_init(description=description, **kwargs)

            # group attributes
            self.title = title
            self._group_actions = []

            # share most attributes with the container
            self._registries = container._registries
            self._actions = container._actions
            self._option_string_actions = container._option_string_actions
            self._defaults = container._defaults
            self._has_negative_number_optionals = \
                container._has_negative_number_optionals

        def _add_action(self, action):
            action = super(_ArgumentGroup, self)._add_action(action)
            self._group_actions.append(action)
            return action

        def _remove_action(self, action):
            super(_ArgumentGroup, self)._remove_action(action)
            self._group_actions.remove(action)


    class _MutuallyExclusiveGroup(_ArgumentGroup):

        def __init__(self, container, required=False):
            super(_MutuallyExclusiveGroup, self).__init__(container)
            self.required = required
            self._container = container

        def _add_action(self, action):
            if action.required:
                msg = _('mutually exclusive arguments must be optional')
                raise ValueError(msg)
            action = self._container._add_action(action)
            self._group_actions.append(action)
            return action

        def _remove_action(self, action):
            self._container._remove_action(action)
            self._group_actions.remove(action)


    class ArgumentParser(_AttributeHolder, _ActionsContainer):
        """Object for parsing command line strings into Python objects.

        Keyword Arguments:
            - prog -- The name of the program (default: sys.argv[0])
            - usage -- A usage message (default: auto-generated from arguments)
            - description -- A description of what the program does
            - epilog -- Text following the argument descriptions
            - parents -- Parsers whose arguments should be copied into this one
            - formatter_class -- HelpFormatter class for printing help messages
            - prefix_chars -- Characters that prefix optional arguments
            - fromfile_prefix_chars -- Characters that prefix files containing
                additional arguments
            - argument_default -- The default value for all arguments
            - conflict_handler -- String indicating how to handle conflicts
            - add_help -- Add a -h/-help option
        """

        def __init__(self,
                     prog=None,
                     usage=None,
                     description=None,
                     epilog=None,
                     version=None,
                     parents=[],
                     formatter_class=HelpFormatter,
                     prefix_chars='-',
                     fromfile_prefix_chars=None,
                     argument_default=None,
                     conflict_handler='error',
                     add_help=True):

            if version is not None:
                import warnings
                warnings.warn(
                    """The "version" argument to ArgumentParser is deprecated. """
                    """Please use """
                    """"add_argument(..., action='version', version="N", ...)" """
                    """instead""", DeprecationWarning)

            superinit = super(ArgumentParser, self).__init__
            superinit(description=description,
                      prefix_chars=prefix_chars,
                      argument_default=argument_default,
                      conflict_handler=conflict_handler)

            # default setting for prog
            if prog is None:
                prog = _os.path.basename(_sys.argv[0])

            self.prog = prog
            self.usage = usage
            self.epilog = epilog
            self.version = version
            self.formatter_class = formatter_class
            self.fromfile_prefix_chars = fromfile_prefix_chars
            self.add_help = add_help

            add_group = self.add_argument_group
            self._positionals = add_group(_('positional arguments'))
            self._optionals = add_group(_('optional arguments'))
            self._subparsers = None

            # register types
            def identity(string):
                return string
            self.register('type', None, identity)

            # add help and version arguments if necessary
            # (using explicit default to override global argument_default)
            if '-' in prefix_chars:
                default_prefix = '-'
            else:
                default_prefix = prefix_chars[0]
            if self.add_help:
                self.add_argument(
                    default_prefix+'h', default_prefix*2+'help',
                    action='help', default=SUPPRESS,
                    help=_('show this help message and exit'))
            if self.version:
                self.add_argument(
                    default_prefix+'v', default_prefix*2+'version',
                    action='version', default=SUPPRESS,
                    version=self.version,
                    help=_("show program's version number and exit"))

            # add parent arguments and defaults
            for parent in parents:
                self._add_container_actions(parent)
                try:
                    defaults = parent._defaults
                except AttributeError:
                    pass
                else:
                    self._defaults.update(defaults)

        # =======================
        # Pretty __repr__ methods
        # =======================
        def _get_kwargs(self):
            names = [
                'prog',
                'usage',
                'description',
                'version',
                'formatter_class',
                'conflict_handler',
                'add_help',
            ]
            return [(name, getattr(self, name)) for name in names]

        # ==================================
        # Optional/Positional adding methods
        # ==================================
        def add_subparsers(self, **kwargs):
            if self._subparsers is not None:
                self.error(_('cannot have multiple subparser arguments'))

            # add the parser class to the arguments if it's not present
            kwargs.setdefault('parser_class', type(self))

            if 'title' in kwargs or 'description' in kwargs:
                title = _(kwargs.pop('title', 'subcommands'))
                description = _(kwargs.pop('description', None))
                self._subparsers = self.add_argument_group(title, description)
            else:
                self._subparsers = self._positionals

            # prog defaults to the usage message of this parser, skipping
            # optional arguments and with no "usage:" prefix
            if kwargs.get('prog') is None:
                formatter = self._get_formatter()
                positionals = self._get_positional_actions()
                groups = self._mutually_exclusive_groups
                formatter.add_usage(self.usage, positionals, groups, '')
                kwargs['prog'] = formatter.format_help().strip()

            # create the parsers action and add it to the positionals list
            parsers_class = self._pop_action_class(kwargs, 'parsers')
            action = parsers_class(option_strings=[], **kwargs)
            self._subparsers._add_action(action)

            # return the created parsers action
            return action

        def _add_action(self, action):
            if action.option_strings:
                self._optionals._add_action(action)
            else:
                self._positionals._add_action(action)
            return action

        def _get_optional_actions(self):
            return [action
                    for action in self._actions
                    if action.option_strings]

        def _get_positional_actions(self):
            return [action
                    for action in self._actions
                    if not action.option_strings]

        # =====================================
        # Command line argument parsing methods
        # =====================================
        def parse_args(self, args=None, namespace=None):
            args, argv = self.parse_known_args(args, namespace)
            if argv:
                msg = _('unrecognized arguments: %s')
                self.error(msg % ' '.join(argv))
            return args

        def parse_known_args(self, args=None, namespace=None):
            # args default to the system args
            if args is None:
                args = _sys.argv[1:]

            # default Namespace built from parser defaults
            if namespace is None:
                namespace = Namespace()

            # add any action defaults that aren't present
            for action in self._actions:
                if action.dest is not SUPPRESS:
                    if not hasattr(namespace, action.dest):
                        if action.default is not SUPPRESS:
                            default = action.default
                            if isinstance(action.default, str):
                                default = self._get_value(action, default)
                            setattr(namespace, action.dest, default)

            # add any parser defaults that aren't present
            for dest in self._defaults:
                if not hasattr(namespace, dest):
                    setattr(namespace, dest, self._defaults[dest])

            # parse the arguments and exit if there are any errors
            try:
                namespace, args = self._parse_known_args(args, namespace)
                if hasattr(namespace, _UNRECOGNIZED_ARGS_ATTR):
                    args.extend(getattr(namespace, _UNRECOGNIZED_ARGS_ATTR))
                    delattr(namespace, _UNRECOGNIZED_ARGS_ATTR)
                return namespace, args
            except ArgumentError:
                err = _sys.exc_info()[1]
                self.error(str(err))

        def _parse_known_args(self, arg_strings, namespace):
            # replace arg strings that are file references
            if self.fromfile_prefix_chars is not None:
                arg_strings = self._read_args_from_files(arg_strings)

            # map all mutually exclusive arguments to the other arguments
            # they can't occur with
            action_conflicts = {}
            for mutex_group in self._mutually_exclusive_groups:
                group_actions = mutex_group._group_actions
                for i, mutex_action in enumerate(mutex_group._group_actions):
                    conflicts = action_conflicts.setdefault(mutex_action, [])
                    conflicts.extend(group_actions[:i])
                    conflicts.extend(group_actions[i + 1:])

            # find all option indices, and determine the arg_string_pattern
            # which has an 'O' if there is an option at an index,
            # an 'A' if there is an argument, or a '-' if there is a '--'
            option_string_indices = {}
            arg_string_pattern_parts = []
            arg_strings_iter = iter(arg_strings)
            for i, arg_string in enumerate(arg_strings_iter):

                # all args after -- are non-options
                if arg_string == '--':
                    arg_string_pattern_parts.append('-')
                    for arg_string in arg_strings_iter:
                        arg_string_pattern_parts.append('A')

                # otherwise, add the arg to the arg strings
                # and note the index if it was an option
                else:
                    option_tuple = self._parse_optional(arg_string)
                    if option_tuple is None:
                        pattern = 'A'
                    else:
                        option_string_indices[i] = option_tuple
                        pattern = 'O'
                    arg_string_pattern_parts.append(pattern)

            # join the pieces together to form the pattern
            arg_strings_pattern = ''.join(arg_string_pattern_parts)

            # converts arg strings to the appropriate and then takes the action
            seen_actions = set()
            seen_non_default_actions = set()

            def take_action(action, argument_strings, option_string=None):
                seen_actions.add(action)
                argument_values = self._get_values(action, argument_strings)

                # error if this argument is not allowed with other previously
                # seen arguments, assuming that actions that use the default
                # value don't really count as "present"
                if argument_values is not action.default:
                    seen_non_default_actions.add(action)
                    for conflict_action in action_conflicts.get(action, []):
                        if conflict_action in seen_non_default_actions:
                            msg = _('not allowed with argument %s')
                            action_name = _get_action_name(conflict_action)
                            raise ArgumentError(action, msg % action_name)

                # take the action if we didn't receive a SUPPRESS value
                # (e.g. from a default)
                if argument_values is not SUPPRESS:
                    action(self, namespace, argument_values, option_string)

            # function to convert arg_strings into an optional action
            def consume_optional(start_index):

                # get the optional identified at this index
                option_tuple = option_string_indices[start_index]
                action, option_string, explicit_arg = option_tuple

                # identify additional optionals in the same arg string
                # (e.g. -xyz is the same as -x -y -z if no args are required)
                match_argument = self._match_argument
                action_tuples = []
                while True:

                    # if we found no optional action, skip it
                    if action is None:
                        extras.append(arg_strings[start_index])
                        return start_index + 1

                    # if there is an explicit argument, try to match the
                    # optional's string arguments to only this
                    if explicit_arg is not None:
                        arg_count = match_argument(action, 'A')

                        # if the action is a single-dash option and takes no
                        # arguments, try to parse more single-dash options out
                        # of the tail of the option string
                        chars = self.prefix_chars
                        if arg_count == 0 and option_string[1] not in chars:
                            action_tuples.append((action, [], option_string))
                            char = option_string[0]
                            option_string = char + explicit_arg[0]
                            new_explicit_arg = explicit_arg[1:] or None
                            optionals_map = self._option_string_actions
                            if option_string in optionals_map:
                                action = optionals_map[option_string]
                                explicit_arg = new_explicit_arg
                            else:
                                msg = _('ignored explicit argument %r')
                                raise ArgumentError(action, msg % explicit_arg)

                        # if the action expect exactly one argument, we've
                        # successfully matched the option; exit the loop
                        elif arg_count == 1:
                            stop = start_index + 1
                            args = [explicit_arg]
                            action_tuples.append((action, args, option_string))
                            break

                        # error if a double-dash option did not use the
                        # explicit argument
                        else:
                            msg = _('ignored explicit argument %r')
                            raise ArgumentError(action, msg % explicit_arg)

                    # if there is no explicit argument, try to match the
                    # optional's string arguments with the following strings
                    # if successful, exit the loop
                    else:
                        start = start_index + 1
                        selected_patterns = arg_strings_pattern[start:]
                        arg_count = match_argument(action, selected_patterns)
                        stop = start + arg_count
                        args = arg_strings[start:stop]
                        action_tuples.append((action, args, option_string))
                        break

                # add the Optional to the list and return the index at which
                # the Optional's string args stopped
                assert action_tuples
                for action, args, option_string in action_tuples:
                    take_action(action, args, option_string)
                return stop

            # the list of Positionals left to be parsed; this is modified
            # by consume_positionals()
            positionals = self._get_positional_actions()

            # function to convert arg_strings into positional actions
            def consume_positionals(start_index):
                # match as many Positionals as possible
                match_partial = self._match_arguments_partial
                selected_pattern = arg_strings_pattern[start_index:]
                arg_counts = match_partial(positionals, selected_pattern)

                # slice off the appropriate arg strings for each Positional
                # and add the Positional and its args to the list
                for action, arg_count in zip(positionals, arg_counts):
                    args = arg_strings[start_index: start_index + arg_count]
                    start_index += arg_count
                    take_action(action, args)

                # slice off the Positionals that we just parsed and return the
                # index at which the Positionals' string args stopped
                positionals[:] = positionals[len(arg_counts):]
                return start_index

            # consume Positionals and Optionals alternately, until we have
            # passed the last option string
            extras = []
            start_index = 0
            if option_string_indices:
                max_option_string_index = max(option_string_indices)
            else:
                max_option_string_index = -1
            while start_index <= max_option_string_index:

                # consume any Positionals preceding the next option
                next_option_string_index = min([
                    index
                    for index in option_string_indices
                    if index >= start_index])
                if start_index != next_option_string_index:
                    positionals_end_index = consume_positionals(start_index)

                    # only try to parse the next optional if we didn't consume
                    # the option string during the positionals parsing
                    if positionals_end_index > start_index:
                        start_index = positionals_end_index
                        continue
                    else:
                        start_index = positionals_end_index

                # if we consumed all the positionals we could and we're not
                # at the index of an option string, there were extra arguments
                if start_index not in option_string_indices:
                    strings = arg_strings[start_index:next_option_string_index]
                    extras.extend(strings)
                    start_index = next_option_string_index

                # consume the next optional and any arguments for it
                start_index = consume_optional(start_index)

            # consume any positionals following the last Optional
            stop_index = consume_positionals(start_index)

            # if we didn't consume all the argument strings, there were extras
            extras.extend(arg_strings[stop_index:])

            # if we didn't use all the Positional objects, there were too few
            # arg strings supplied.
            if positionals:
                self.error(_('too few arguments'))

            # make sure all required actions were present
            for action in self._actions:
                if action.required:
                    if action not in seen_actions:
                        name = _get_action_name(action)
                        self.error(_('argument %s is required') % name)

            # make sure all required groups had one option present
            for group in self._mutually_exclusive_groups:
                if group.required:
                    for action in group._group_actions:
                        if action in seen_non_default_actions:
                            break

                    # if no actions were used, report the error
                    else:
                        names = [_get_action_name(action)
                                 for action in group._group_actions
                                 if action.help is not SUPPRESS]
                        msg = _('one of the arguments %s is required')
                        self.error(msg % ' '.join(names))

            # return the updated namespace and the extra arguments
            return namespace, extras

        def _read_args_from_files(self, arg_strings):
            # expand arguments referencing files
            new_arg_strings = []
            for arg_string in arg_strings:

                # for regular arguments, just add them back into the list
                if arg_string[0] not in self.fromfile_prefix_chars:
                    new_arg_strings.append(arg_string)

                # replace arguments referencing files with the file content
                else:
                    try:
                        args_file = open(arg_string[1:])
                        try:
                            arg_strings = []
                            for arg_line in args_file.read().splitlines():
                                for arg in self.convert_arg_line_to_args(arg_line):
                                    arg_strings.append(arg)
                            arg_strings = self._read_args_from_files(arg_strings)
                            new_arg_strings.extend(arg_strings)
                        finally:
                            args_file.close()
                    except IOError:
                        err = _sys.exc_info()[1]
                        self.error(str(err))

            # return the modified argument list
            return new_arg_strings

        def convert_arg_line_to_args(self, arg_line):
            return [arg_line]

        def _match_argument(self, action, arg_strings_pattern):
            # match the pattern for this action to the arg strings
            nargs_pattern = self._get_nargs_pattern(action)
            match = _re.match(nargs_pattern, arg_strings_pattern)

            # raise an exception if we weren't able to find a match
            if match is None:
                nargs_errors = {
                    None: _('expected one argument'),
                    OPTIONAL: _('expected at most one argument'),
                    ONE_OR_MORE: _('expected at least one argument'),
                }
                default = _('expected %s argument(s)') % action.nargs
                msg = nargs_errors.get(action.nargs, default)
                raise ArgumentError(action, msg)

            # return the number of arguments matched
            return len(match.group(1))

        def _match_arguments_partial(self, actions, arg_strings_pattern):
            # progressively shorten the actions list by slicing off the
            # final actions until we find a match
            result = []
            for i in range(len(actions), 0, -1):
                actions_slice = actions[:i]
                pattern = ''.join([self._get_nargs_pattern(action)
                                   for action in actions_slice])
                match = _re.match(pattern, arg_strings_pattern)
                if match is not None:
                    result.extend([len(string) for string in match.groups()])
                    break

            # return the list of arg string counts
            return result

        def _parse_optional(self, arg_string):
            # if it's an empty string, it was meant to be a positional
            if not arg_string:
                return None

            # if it doesn't start with a prefix, it was meant to be positional
            if not arg_string[0] in self.prefix_chars:
                return None

            # if the option string is present in the parser, return the action
            if arg_string in self._option_string_actions:
                action = self._option_string_actions[arg_string]
                return action, arg_string, None

            # if it's just a single character, it was meant to be positional
            if len(arg_string) == 1:
                return None

            # if the option string before the "=" is present, return the action
            if '=' in arg_string:
                option_string, explicit_arg = arg_string.split('=', 1)
                if option_string in self._option_string_actions:
                    action = self._option_string_actions[option_string]
                    return action, option_string, explicit_arg

            # search through all possible prefixes of the option string
            # and all actions in the parser for possible interpretations
            option_tuples = self._get_option_tuples(arg_string)

            # if multiple actions match, the option string was ambiguous
            if len(option_tuples) > 1:
                options = ', '.join([option_string
                    for action, option_string, explicit_arg in option_tuples])
                tup = arg_string, options
                self.error(_('ambiguous option: %s could match %s') % tup)

            # if exactly one action matched, this segmentation is good,
            # so return the parsed action
            elif len(option_tuples) == 1:
                option_tuple, = option_tuples
                return option_tuple

            # if it was not found as an option, but it looks like a negative
            # number, it was meant to be positional
            # unless there are negative-number-like options
            if self._negative_number_matcher.match(arg_string):
                if not self._has_negative_number_optionals:
                    return None

            # if it contains a space, it was meant to be a positional
            if ' ' in arg_string:
                return None

            # it was meant to be an optional but there is no such option
            # in this parser (though it might be a valid option in a subparser)
            return None, arg_string, None

        def _get_option_tuples(self, option_string):
            result = []

            # option strings starting with two prefix characters are only
            # split at the '='
            chars = self.prefix_chars
            if option_string[0] in chars and option_string[1] in chars:
                if '=' in option_string:
                    option_prefix, explicit_arg = option_string.split('=', 1)
                else:
                    option_prefix = option_string
                    explicit_arg = None
                for option_string in self._option_string_actions:
                    if option_string.startswith(option_prefix):
                        action = self._option_string_actions[option_string]
                        tup = action, option_string, explicit_arg
                        result.append(tup)

            # single character options can be concatenated with their arguments
            # but multiple character options always have to have their argument
            # separate
            elif option_string[0] in chars and option_string[1] not in chars:
                option_prefix = option_string
                explicit_arg = None
                short_option_prefix = option_string[:2]
                short_explicit_arg = option_string[2:]

                for option_string in self._option_string_actions:
                    if option_string == short_option_prefix:
                        action = self._option_string_actions[option_string]
                        tup = action, option_string, short_explicit_arg
                        result.append(tup)
                    elif option_string.startswith(option_prefix):
                        action = self._option_string_actions[option_string]
                        tup = action, option_string, explicit_arg
                        result.append(tup)

            # shouldn't ever get here
            else:
                self.error(_('unexpected option string: %s') % option_string)

            # return the collected option tuples
            return result

        def _get_nargs_pattern(self, action):
            # in all examples below, we have to allow for '--' args
            # which are represented as '-' in the pattern
            nargs = action.nargs

            # the default (None) is assumed to be a single argument
            if nargs is None:
                nargs_pattern = '(-*A-*)'

            # allow zero or one arguments
            elif nargs == OPTIONAL:
                nargs_pattern = '(-*A?-*)'

            # allow zero or more arguments
            elif nargs == ZERO_OR_MORE:
                nargs_pattern = '(-*[A-]*)'

            # allow one or more arguments
            elif nargs == ONE_OR_MORE:
                nargs_pattern = '(-*A[A-]*)'

            # allow any number of options or arguments
            elif nargs == REMAINDER:
                nargs_pattern = '([-AO]*)'

            # allow one argument followed by any number of options or arguments
            elif nargs == PARSER:
                nargs_pattern = '(-*A[-AO]*)'

            # all others should be integers
            else:
                nargs_pattern = '(-*%s-*)' % '-*'.join('A' * nargs)

            # if this is an optional action, -- is not allowed
            if action.option_strings:
                nargs_pattern = nargs_pattern.replace('-*', '')
                nargs_pattern = nargs_pattern.replace('-', '')

            # return the pattern
            return nargs_pattern

        # ========================
        # Value conversion methods
        # ========================
        def _get_values(self, action, arg_strings):
            # for everything but PARSER args, strip out '--'
            if action.nargs not in [PARSER, REMAINDER]:
                arg_strings = [s for s in arg_strings if s != '--']

            # optional argument produces a default when not present
            if not arg_strings and action.nargs == OPTIONAL:
                if action.option_strings:
                    value = action.const
                else:
                    value = action.default
                if isinstance(value, str):
                    value = self._get_value(action, value)
                    self._check_value(action, value)

            # when nargs='*' on a positional, if there were no command-line
            # args, use the default if it is anything other than None
            elif (not arg_strings and action.nargs == ZERO_OR_MORE and
                  not action.option_strings):
                if action.default is not None:
                    value = action.default
                else:
                    value = arg_strings
                self._check_value(action, value)

            # single argument or optional argument produces a single value
            elif len(arg_strings) == 1 and action.nargs in [None, OPTIONAL]:
                arg_string, = arg_strings
                value = self._get_value(action, arg_string)
                self._check_value(action, value)

            # REMAINDER arguments convert all values, checking none
            elif action.nargs == REMAINDER:
                value = [self._get_value(action, v) for v in arg_strings]

            # PARSER arguments convert all values, but check only the first
            elif action.nargs == PARSER:
                value = [self._get_value(action, v) for v in arg_strings]
                self._check_value(action, value[0])

            # all other types of nargs produce a list
            else:
                value = [self._get_value(action, v) for v in arg_strings]
                for v in value:
                    self._check_value(action, v)

            # return the converted value
            return value

        def _get_value(self, action, arg_string):
            type_func = self._registry_get('type', action.type, action.type)
            if not _callable(type_func):
                msg = _('%r is not callable')
                raise ArgumentError(action, msg % type_func)

            # convert the value to the appropriate type
            try:
                result = type_func(arg_string)

            # ArgumentTypeErrors indicate errors
            except ArgumentTypeError:
                name = getattr(action.type, '__name__', repr(action.type))
                msg = str(_sys.exc_info()[1])
                raise ArgumentError(action, msg)

            # TypeErrors or ValueErrors also indicate errors
            except (TypeError, ValueError):
                name = getattr(action.type, '__name__', repr(action.type))
                msg = _('invalid %s value: %r')
                raise ArgumentError(action, msg % (name, arg_string))

            # return the converted value
            return result

        def _check_value(self, action, value):
            # converted value must be one of the choices (if specified)
            if action.choices is not None and value not in action.choices:
                tup = value, ', '.join(map(repr, action.choices))
                msg = _('invalid choice: %r (choose from %s)') % tup
                raise ArgumentError(action, msg)

        # =======================
        # Help-formatting methods
        # =======================
        def format_usage(self):
            formatter = self._get_formatter()
            formatter.add_usage(self.usage, self._actions,
                                self._mutually_exclusive_groups)
            return formatter.format_help()

        def format_help(self):
            formatter = self._get_formatter()

            # usage
            formatter.add_usage(self.usage, self._actions,
                                self._mutually_exclusive_groups)

            # description
            formatter.add_text(self.description)

            # positionals, optionals and user-defined groups
            for action_group in self._action_groups:
                formatter.start_section(action_group.title)
                formatter.add_text(action_group.description)
                formatter.add_arguments(action_group._group_actions)
                formatter.end_section()

            # epilog
            formatter.add_text(self.epilog)

            # determine help from format above
            return formatter.format_help()

        def format_version(self):
            import warnings
            warnings.warn(
                'The format_version method is deprecated -- the "version" '
                'argument to ArgumentParser is no longer supported.',
                DeprecationWarning)
            formatter = self._get_formatter()
            formatter.add_text(self.version)
            return formatter.format_help()

        def _get_formatter(self):
            return self.formatter_class(prog=self.prog)

        # =====================
        # Help-printing methods
        # =====================
        def print_usage(self, file=None):
            if file is None:
                file = _sys.stdout
            self._print_message(self.format_usage(), file)

        def print_help(self, file=None):
            if file is None:
                file = _sys.stdout
            self._print_message(self.format_help(), file)

        def print_version(self, file=None):
            import warnings
            warnings.warn(
                'The print_version method is deprecated -- the "version" '
                'argument to ArgumentParser is no longer supported.',
                DeprecationWarning)
            self._print_message(self.format_version(), file)

        def _print_message(self, message, file=None):
            if message:
                if file is None:
                    file = _sys.stderr
                file.write(message)

        # ===============
        # Exiting methods
        # ===============
        def exit(self, status=0, message=None):
            if message:
                self._print_message(message, _sys.stderr)
            _sys.exit(status)

        def error(self, message):
            """error(message: string)

            Prints a usage message incorporating the message to stderr and
            exits.

            If you override this in a subclass, it should not return -- it
            should either exit or raise an exception.
            """
            self.print_usage(_sys.stderr)
            self.exit(2, _('%s: error: %s\n') % (self.prog, message))
