Gets any data object replica that are marked as out of date/not in date.
        :return: the out of data object replica

def get_out_of_date(self) -> Sequence[DataObjectReplica]:
        """
        Gets any data object replica that are marked as out of date/not in date.
        :return: the out of data object replica
        """
        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