code: def _anonymous_match(self, struct1, struct2, fu, s1_supercell=True,
                           use_rms=False, break_on_match=False, single_match=False):
          
          if not isinstance(self._comparator, SpeciesComparator):
              raise ValueError('Anonymous fitting currently requires SpeciesComparator')
  
          # check that species lists are comparable
          sp1 = struct1.composition.elements
          sp2 = struct2.composition.elements
          if len(sp1) != len(sp2):
              return None
  
          ratio = fu if s1_supercell else 1/fu
          swapped = len(struct1) * ratio < len(struct2)
  
          s1_comp = struct1.composition
          s2_comp = struct2.composition
          matches = []
          for perm in itertools.permutations(sp2):
              sp_mapping = dict(zip(sp1, perm))
  
              # do quick check that compositions are compatible
              mapped_comp = Composition({sp_mapping[k]: v
                                         for k, v in s1_comp.items()})
              if (not self._subset) and (
                      self._comparator.get_hash(mapped_comp) !=
                      self._comparator.get_hash(s2_comp)):
                  continue
  
              mapped_struct = struct1.copy()
              mapped_struct.replace_species(sp_mapping)
              if swapped:
                  m = self._strict_match(struct2, mapped_struct, fu,
                                         (not s1_supercell), use_rms,
                                         break_on_match)
              else:
                  m = self._strict_match(mapped_struct, struct2, fu, s1_supercell,
                                         use_rms, break_on_match)
              if m:
                  matches.append((sp_mapping, m))
                  if single_match:
                      break
          return matches
docs: Tries all permutations of matching struct1 to struct2.
          Args:
              struct1, struct2 (Structure): Preprocessed input structures
          Returns:
              List of (mapping, match)