docs: def get_mzid_specfile_ids(mzidfn, namespace):
      """Returns mzid spectra data filenames and their IDs used in the
      mzIdentML file as a dict. Keys == IDs, values == fns"""
      sid_fn = {}
      for specdata in mzid_specdata_generator(mzidfn, namespace):
          sid_fn[specdata.attrib['id']] = specdata.attrib['name']
      return sid_fn