@Override
    public java.util.concurrent.Future<ListInstancesResult> listInstancesAsync(ListInstancesRequest request) {

        return listInstancesAsync(request, null);
    }
Simplified method form for invoking the ListClusters operation with an AsyncHandler.

@see #listClustersAsync(ListClustersRequest, com.amazonaws.handlers.AsyncHandler)
aws-java-sdk-emr/src/main/java/com/amazonaws/services/elasticmapreduce/AbstractAmazonElasticMapReduceAsync.java