code: def append_with(self, obj, **properties):
          '''Add an item to the dictionary with the given metadata properties'''
          for prop, val in properties.items():
              val = self.serialize(val)
              self._meta.setdefault(prop, {}).setdefault(val, []).append(obj)
          self.append(objf append_with(self, obj, **properties):
          '''Add an item to the dictionary with the given metadata properties'''
          for prop, val in properties.items():
              val = self.serialize(val)
              self._meta.setdefault(prop, {}).setdefault(val, []).append(obj)
          self.append(obj)
docs: Add an item to the dictionary with the given metadata properties