def wait_for_batches(self, batch_ids, timeout=None):
        """Locks until a list of batch ids is committed to the block chain
        or a timeout is exceeded. Returns the statuses of those batches.

        Args:
            batch_ids (list of str): The ids of the batches to wait for
            timeout(int): Maximum time in seconds to wait for

        Returns:
            list of BatchStatus: BatchStatuses to send back to client
        """
        self._batch_tracker.watch_statuses(self, batch_ids)
        timeout = timeout or DEFAULT_TIMEOUT
        start_time = time()

        with self._wait_condition:
            while True:
                if self._statuses is not None:
                    return _format_batch_statuses(
                        self._statuses, batch_ids, self._batch_tracker)

                if time() - start_time > timeout:
                    statuses = self._batch_tracker.get_statuses(batch_ids)
                    return _format_batch_statuses(
                        statuses, batch_ids, self._batch_tracker)

                self._wait_condition.wait(timeout - (time() - start_time))
Locks until a list of batch ids is committed to the block chain
        or a timeout is exceeded. Returns the statuses of those batches.

        Args:
            batch_ids (list of str): The ids of the batches to wait for
            timeout(int): Maximum time in seconds to wait for

        Returns:
            list of BatchStatus: BatchStatuses to send back to client