code: @Override
      public DescribeContainerInstancesResult describeContainerInstances(DescribeContainerInstancesRequest request) {
          request = beforeClientExecution(request);
          return executeDescribeContainerInstances(request);
      }
docs: <p>
  Describes Amazon Elastic Container Service container instances. Returns metadata about registered and remaining
  resources on each container instance requested.
  </p>
  
  @param describeContainerInstancesRequest
  @return Result of the DescribeContainerInstances operation returned by the service.
  @throws ServerException
  These errors are usually caused by a server issue.
  @throws ClientException
  These errors are usually caused by a client action, such as using an action or resource on behalf of a
  user that doesn't have permissions to use the action or resource, or specifying an identifier that is not
  valid.
  @throws InvalidParameterException
  The specified parameter is invalid. Review the available parameters for the API request.
  @throws ClusterNotFoundException
  The specified cluster could not be found. You can view your available clusters with <a>ListClusters</a>.
  Amazon ECS clusters are Region-specific.
  @sample AmazonECS.DescribeContainerInstances
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/ecs-2014-11-13/DescribeContainerInstances" target="_top">AWS
  API Documentation</a>