code: public Observable<Void> resizeAsync(String resourceGroupName, String clusterName) {
          return resizeWithServiceResponseAsync(resourceGroupName, clusterName).map(new Func1<ServiceResponse<Void>, Void>() {
              @Override
              public Void call(ServiceResponse<Void> response) {
                  return response.body();
              }
          });
      }
docs: Resizes the specified HDInsight cluster to the specified size.
  
  @param resourceGroupName The name of the resource group.
  @param clusterName The name of the cluster.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable for the request