code: public Observable<Page<TopicInner>> listAsync() {
          return listWithServiceResponseAsync().map(new Func1<ServiceResponse<List<TopicInner>>, Page<TopicInner>>() {
              @Override
              public Page<TopicInner> call(ServiceResponse<List<TopicInner>> response) {
                  PageImpl<TopicInner> page = new PageImpl<>();
                  page.setItems(response.body());
                  return page;
              }
          });
      }
docs: List topics under an Azure subscription.
  List all the topics under an Azure subscription.
  
  @return the observable to the List&lt;TopicInner&gt; object