Encode an OffsetCommitRequest struct

        Arguments:
            group: string, the consumer group you are committing offsets for
            payloads: list of OffsetCommitRequestPayload

def encode_offset_commit_request(cls, group, payloads):
        """
        Encode an OffsetCommitRequest struct

        Arguments:
            group: string, the consumer group you are committing offsets for
            payloads: list of OffsetCommitRequestPayload
        """
        return kafka.protocol.commit.OffsetCommitRequest[0](
            consumer_group=group,
            topics=[(
                topic,
                [(
                    partition,
                    payload.offset,
                    payload.metadata)
                for partition, payload in six.iteritems(topic_payloads)])
            for topic, topic_payloads in six.iteritems(group_by_topic_and_partition(payloads))])