How to use the rhea.message.data_section function in rhea

}
        for (let index = 0; index < propsCount; index++) {
          const item = props.getItem(index);
          if (!!item) {
            /*Codes_SRS_NODE_IOTHUB_AMQPMSG_16_013: [If one of the property key is `IoThub-status`, this property is reserved and shall be forced to an `int` `rhea` type.]*/
            const val = (item.key === 'IoThub-status') ? rheaTypes.wrap_int(parseInt(item.value)) : item.value;
            amqpMessage.application_properties[item.key] = val;
          }
        }
      }
    }

    /*Codes_SRS_NODE_IOTHUB_AMQPMSG_05_005: [If message.getData() is truthy, the AmqpMessage object shall have a property named body with the value returned from message.getData().]*/
    const body = message.getData();
    if (body !== undefined) {
      amqpMessage.body = rheaMessage.data_section(message.getBytes());
    }

    /*Codes_SRS_NODE_IOTHUB_AMQPMSG_05_006: [The generated AmqpMessage object shall be returned to the caller.]*/
    return amqpMessage;
  }

let requestMessage = new AmqpMessage();
            /*Codes_SRS_NODE_PROVISIONING_AMQP_06_003: [ The `registrationRequest` will send a body in the message which contains a stringified JSON object with a `registrationId` property.] */
            let requestBody: DeviceRegistration = {registrationId: request.registrationId};
            /*Codes_SRS_NODE_PROVISIONING_AMQP_06_004: [The `registrationRequest` will, if utilizing TPM attestation, send a `tpm` property with the endorsement and storage key in the JSON body.] */
            if (this._endorsementKey) {
              requestBody.tpm = {endorsementKey: this._endorsementKey.toString('base64')};
              if (this._storageRootKey) {
                requestBody.tpm.storageRootKey = this._storageRootKey.toString('base64');
              }
            }
            /*Codes_SRS_NODE_PROVISIONING_AMQP_06_005: [The `registrationRequest` will, if utilizing custom allocation data, send a `payload` property in the JSON body.] */
            if (request.payload) {
              requestBody.payload = request.payload;
            }
            requestMessage.body = rheaMessage.data_section(Buffer.from(JSON.stringify(requestBody)));
            requestMessage.application_properties = {};
            requestMessage.application_properties[MessagePropertyNames.OperationType] = DeviceOperations.Register;
            requestMessage.application_properties[MessagePropertyNames.ForceRegistration] = !!request.forceRegistration;
            requestMessage.correlation_id = correlationId;

            debug('initial registration request: ' + JSON.stringify(requestMessage));
            this._operations[requestMessage.correlation_id] = callback;
            this._senderLink.send(requestMessage, (err) => {
              if (err) {
                delete this._operations[requestMessage.correlation_id];
                const translatedError = translateError('registration failure', err);
                /*Codes_SRS_NODE_PROVISIONING_AMQP_06_007: [If the `registrationRequest` send request is rejected with an `InternalError` or `ThrottlingError`, the result.status value will be set with `registering` and the callback will be invoked with *no* error object.] */
                if ((translatedError instanceof errors.InternalServerError) || ((translatedError as AmqpTransportError) instanceof errors.ThrottlingError)) {
                  debug('retryable error on registration: ' + err.name);
                  let retryAfterInMilliseconds: number;
                  /*Codes_SRS_NODE_PROVISIONING_AMQP_06_009: [If the `registrationRequest` rejection error contains the info property`retry-after`, it will be interpreted as the number of seconds that should elapse before the next attempted operation.  Otherwise default.] */