Return an object which wraps a batch read / query.

        :type read_timestamp: :class:`datetime.datetime`
        :param read_timestamp: Execute all reads at the given timestamp.

        :type exact_staleness: :class:`datetime.timedelta`
        :param exact_staleness: Execute all reads at a timestamp that is
                                ``exact_staleness`` old.

        :rtype: :class:`~google.cloud.spanner_v1.database.BatchSnapshot`
        :returns: new wrapper

def batch_snapshot(self, read_timestamp=None, exact_staleness=None):
        """Return an object which wraps a batch read / query.

        :type read_timestamp: :class:`datetime.datetime`
        :param read_timestamp: Execute all reads at the given timestamp.

        :type exact_staleness: :class:`datetime.timedelta`
        :param exact_staleness: Execute all reads at a timestamp that is
                                ``exact_staleness`` old.

        :rtype: :class:`~google.cloud.spanner_v1.database.BatchSnapshot`
        :returns: new wrapper
        """
        return BatchSnapshot(
            self, read_timestamp=read_timestamp, exact_staleness=exact_staleness
        )