Converts the union into a single GC rule as a protobuf.

        :rtype: :class:`.table_v2_pb2.GcRule`
        :returns: The converted current object.

def to_pb(self):
        """Converts the union into a single GC rule as a protobuf.

        :rtype: :class:`.table_v2_pb2.GcRule`
        :returns: The converted current object.
        """
        union = table_v2_pb2.GcRule.Union(rules=[rule.to_pb() for rule in self.rules])
        return table_v2_pb2.GcRule(union=union)