code: @Override
      public DescribeVTLDevicesResult describeVTLDevices(DescribeVTLDevicesRequest request) {
          request = beforeClientExecution(request);
          return executeDescribeVTLDevices(request);
      }
docs: <p>
  Returns a description of virtual tape library (VTL) devices for the specified tape gateway. In the response, AWS
  Storage Gateway returns VTL device information.
  </p>
  <p>
  This operation is only supported in the tape gateway type.
  </p>
  
  @param describeVTLDevicesRequest
  DescribeVTLDevicesInput
  @return Result of the DescribeVTLDevices operation returned by the service.
  @throws InvalidGatewayRequestException
  An exception occurred because an invalid gateway request was issued to the service. For more information,
  see the error and message fields.
  @throws InternalServerErrorException
  An internal server error has occurred during the request. For more information, see the error and message
  fields.
  @sample AWSStorageGateway.DescribeVTLDevices
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/storagegateway-2013-06-30/DescribeVTLDevices"
  target="_top">AWS API Documentation</a>