Sends the current. batch to Cloud Bigtable.
        For example:

        .. literalinclude:: snippets.py
            :start-after: [START bigtable_batcher_flush]
            :end-before: [END bigtable_batcher_flush]

def flush(self):
        """ Sends the current. batch to Cloud Bigtable.
        For example:

        .. literalinclude:: snippets.py
            :start-after: [START bigtable_batcher_flush]
            :end-before: [END bigtable_batcher_flush]

        """
        if len(self.rows) != 0:
            self.table.mutate_rows(self.rows)
            self.total_mutation_count = 0
            self.total_size = 0
            self.rows = []