docs: public Observable<RegistryUsageListResultInner> listUsagesAsync(String resourceGroupName, String registryName) {
          return listUsagesWithServiceResponseAsync(resourceGroupName, registryName).map(new Func1<ServiceResponse<RegistryUsageListResultInner>, RegistryUsageListResultInner>() {
              @Override
              public RegistryUsageListResultInner call(ServiceResponse<RegistryUsageListResultInner> response) {
                  return response.body();
              }
          });
      }