Encode a ConsumerMetadataRequest

        Arguments:
            client_id: string
            correlation_id: int
            payloads: string (consumer group)

def encode_consumer_metadata_request(cls, client_id, correlation_id, payloads):
        """
        Encode a ConsumerMetadataRequest

        Arguments:
            client_id: string
            correlation_id: int
            payloads: string (consumer group)
        """
        message = []
        message.append(cls._encode_message_header(client_id, correlation_id,
                                                  KafkaProtocol.CONSUMER_METADATA_KEY))
        message.append(struct.pack('>h%ds' % len(payloads), len(payloads), payloads))

        msg = b''.join(message)
        return write_int_string(msg)