docs: def _idFromHeaderInfo(headerInfo, isDecoy, decoyTag):
      """Generates a protein id from headerInfo. If "isDecoy" is True, the
      "decoyTag" is added to beginning of the generated protein id.
  
      :param headerInfo: dict, must contain a key "id"
      :param isDecoy: bool, determines if the "decoyTag" is added or not.
      :param decoyTag: str, a tag that identifies decoy / reverse protein entries.
      :returns: str, protein id
      """
      proteinId = headerInfo['id']
      if isDecoy:
          proteinId = ''.join((decoyTag, proteinId))
  
      return proteinId