code: @Override
      public DiscoverInstancesResult discoverInstances(DiscoverInstancesRequest request) {
          request = beforeClientExecution(request);
          return executeDiscoverInstances(request);
      }
docs: <p>
  Discovers registered instances for a specified namespace and service.
  </p>
  
  @param discoverInstancesRequest
  @return Result of the DiscoverInstances operation returned by the service.
  @throws ServiceNotFoundException
  No service exists with the specified ID.
  @throws NamespaceNotFoundException
  No namespace exists with the specified ID.
  @throws InvalidInputException
  One or more specified values aren't valid. For example, a required value might be missing, a numeric
  value might be outside the allowed range, or a string value might exceed length constraints.
  @sample AWSServiceDiscovery.DiscoverInstances
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/servicediscovery-2017-03-14/DiscoverInstances"
  target="_top">AWS API Documentation</a>