docs: public Observable<DiskInner> getByResourceGroupAsync(String resourceGroupName, String diskName) {
          return getByResourceGroupWithServiceResponseAsync(resourceGroupName, diskName).map(new Func1<ServiceResponse<DiskInner>, DiskInner>() {
              @Override
              public DiskInner call(ServiceResponse<DiskInner> response) {
                  return response.body();
              }
          });
      }