code: @Override
      public DescribeListenersResult describeListeners(DescribeListenersRequest request) {
          request = beforeClientExecution(request);
          return executeDescribeListeners(request);
      }
docs: <p>
  Describes the specified listeners or the listeners for the specified Application Load Balancer or Network Load
  Balancer. You must specify either a load balancer or one or more listeners.
  </p>
  
  @param describeListenersRequest
  @return Result of the DescribeListeners operation returned by the service.
  @throws ListenerNotFoundException
  The specified listener does not exist.
  @throws LoadBalancerNotFoundException
  The specified load balancer does not exist.
  @throws UnsupportedProtocolException
  The specified protocol is not supported.
  @sample AmazonElasticLoadBalancing.DescribeListeners
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/elasticloadbalancingv2-2015-12-01/DescribeListeners"
  target="_top">AWS API Documentation</a>