code: def append_filter(self, structure_filter):
          
          hdict = structure_filter.as_dict()
          hdict["input_structure"] = self.final_structure.as_dict()
          self.history.append(hdict)
docs: Adds a filter.
  
          Args:
              structure_filter (StructureFilter): A filter implementating the
                  AbstractStructureFilter API. Tells transmuter waht structures
                  to retain.