docs: def _validate_id_types(self):
          '''Check that the ID types are integers for Rosetta, SEQRES, and UniParc sequences and 6-character PDB IDs for the ATOM sequences.'''
  
          for sequences in [self.uniparc_sequences, self.fasta_sequences, self.seqres_sequences, self.rosetta_sequences]:
              for chain_id, sequence in sequences.iteritems():
                  sequence_id_types = set(map(type, sequence.ids()))
                  if sequence_id_types:
                      assert(len(sequence_id_types) == 1)
                      assert(sequence_id_types.pop() == types.IntType)
  
          for chain_id, sequence in self.atom_sequences.iteritems():
              sequence_id_types = set(map(type, sequence.ids()))
              assert(len(sequence_id_types) == 1)
              sequence_id_type = sequence_id_types.pop()
              assert(sequence_id_type == types.StringType or sequence_id_type == types.UnicodeType)