# command
humann2_rna_dna_norm -d rna_dna_norm-dna.txt -r rna_dna_norm-rna.txt -o rna_dna_norm -m witten_bell
# output:
# 1) rna_dna_norm-smoothed_dna.txt
# 2) rna_dna_norm-smoothed_rna.txt
# 1) rna_dna_norm-relative_expression.txt
