code: def _mergeProteinEntries(proteinLists, protToPeps):
      mergedProtToPeps = dict(protToPeps)
      for proteins in proteinLists:
          for protein in proteins:
              peptides = mergedProtToPeps.pop(protein)
          mergedProtein = tuple(sorted(proteins))
          mergedProtToPeps[mergedProtein] = peptides
      return mergedProtToPeps