code: public ServiceFuture<List<FeatureResultInner>> list1Async(final String resourceProviderNamespace, final ListOperationCallback<FeatureResultInner> serviceCallback) {
          return AzureServiceFuture.fromPageResponse(
              list1SinglePageAsync(resourceProviderNamespace),
              new Func1<String, Observable<ServiceResponse<Page<FeatureResultInner>>>>() {
                  @Override
                  public Observable<ServiceResponse<Page<FeatureResultInner>>> call(String nextPageLink) {
                      return list1NextSinglePageAsync(nextPageLink);
                  }
              },
              serviceCallback);
      }
docs: Gets all the preview features in a provider namespace that are available through AFEC for the subscription.
  
  @param resourceProviderNamespace The namespace of the resource provider for getting features.
  @param serviceCallback the async ServiceCallback to handle successful and failed responses.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the {@link ServiceFuture} object