code: def get_out_of_date(self) -> Sequence[DataObjectReplica]:
          
          out_of_date = []
          for number, data_object_replica in self._data.items():
              if not data_object_replica.up_to_date:
                  out_of_date.append(data_object_replica)
          return out_of_date
docs: Gets any data object replica that are marked as out of date/not in date.
          :return: the out of data object replica