docs: def get_differing_atom_residue_ids(self, pdb_name, pdb_list):
          '''Returns a list of residues in pdb_name which differ from the pdbs corresponding to the names in pdb_list.'''
  
          assert(pdb_name in self.pdb_names)
          assert(set(pdb_list).intersection(set(self.pdb_names)) == set(pdb_list)) # the names in pdb_list must be in pdb_names
  
          differing_atom_residue_ids = set()
          for other_pdb in pdb_list:
              differing_atom_residue_ids = differing_atom_residue_ids.union(set(self.differing_atom_residue_ids[(pdb_name, other_pdb)]))
  
          return sorted(differing_atom_residue_ids)