# StorageAttribute

class `openff.evaluator.storage.attributes.``StorageAttribute`(docstring, type_hint, optional=False)

  A descriptor used to mark attributes of a class as those which store information about a cached piece of data.

  `__init__`(docstring, type_hint, optional=False)

    Initializes a new Attribute object.

    Parameters

      - docstring (str) – A docstring describing the attributes purpose. This will automatically be decorated with additional information such as type hints, default values, etc.

      - type_hint (type , typing.Union) – The expected type of this attribute. This will be used to help the workflow engine ensure that expected input types match corresponding output values.

      - default_value (Any) – The default value for this attribute.

      - optional (bool) – Defines whether this is an optional input of a class. If true, the default_value should be set to UNDEFINED.

      - read_only (bool) – Defines whether this attribute is read-only.

  Methods

  `__init__`(docstring, type_hint[, optional]) | Initializes a new Attribute object.