docs: function(params, messages, cb) {
      var correlationId = _cbt.put(prodResponse(cb));
      var msg = envelope(prod.encode()
                             .correlation(correlationId)
                             .client(_options.clientId)
                             .timeout()
                             .topic(params.topic)
                             .partition(params.partition)
                             .messages(messages)
                             .end());
      sendMsg(msg, correlationId, cb);
    }