code: def _flattenMergedProteins(proteins):
      
      proteinSet = set()
      for protein in proteins:
          if isinstance(protein, tuple):
              proteinSet.update(protein)
          else:
              proteinSet.add(protein)
      return proteinSet
docs: Return a set where merged protein entries in proteins are flattened.
  
      :param proteins: an iterable of proteins, can contain merged protein entries
          in the form of tuple([protein1, protein2]).
      returns a set of protein entries, where all entries are strings