code: public Observable<Page<RegistryInner>> listAsync() {
          return listWithServiceResponseAsync()
              .map(new Func1<ServiceResponse<Page<RegistryInner>>, Page<RegistryInner>>() {
                  @Override
                  public Page<RegistryInner> call(ServiceResponse<Page<RegistryInner>> response) {
                      return response.body();
                  }
              });
      }
docs: Lists all the container registries under the specified subscription.
  
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the PagedList&lt;RegistryInner&gt; object