docs: def get_pepproteins(line):
      """Returns from a PSM line peptide sequence,
      and other information about the PSM.
      Return values:
          psm_id          -   str
          proteins        -   list of str
      """
      psm_id = get_psm_id(line)
      proteins = get_proteins_from_psm(line)
      return psm_id, proteins