def get_by_number(self, number: int) -> Optional[DataObjectReplica]:
        """
        Gets the data object replica in this collection with the given number. Will return `None` if such replica does
        not exist.
        :param number: the number of the data object replica to get
        :return: the data object replica in this collection with the given number
        """
        return self._data.get(number, None)