code: @Override
      public DescribeListenerResult describeListener(DescribeListenerRequest request) {
          request = beforeClientExecution(request);
          return executeDescribeListener(request);
      }
docs: <p>
  Describe a listener.
  </p>
  
  @param describeListenerRequest
  @return Result of the DescribeListener operation returned by the service.
  @throws InvalidArgumentException
  An argument that you specified is invalid.
  @throws ListenerNotFoundException
  The listener that you specified doesn't exist.
  @throws InternalServiceErrorException
  There was an internal error for AWS Global Accelerator.
  @sample AWSGlobalAccelerator.DescribeListener
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/globalaccelerator-2018-08-08/DescribeListener"
  target="_top">AWS API Documentation</a>