Counts flow results of a given flow using given query options.

def CountFlowResults(self, client_id, flow_id, with_tag=None, with_type=None):
    """Counts flow results of a given flow using given query options."""
    return len(
        self.ReadFlowResults(
            client_id,
            flow_id,
            0,
            sys.maxsize,
            with_tag=with_tag,
            with_type=with_type))