code: public Observable<Page<MediaServiceInner>> listByResourceGroupAsync(String resourceGroupName) {
          return listByResourceGroupWithServiceResponseAsync(resourceGroupName).map(new Func1<ServiceResponse<List<MediaServiceInner>>, Page<MediaServiceInner>>() {
              @Override
              public Page<MediaServiceInner> call(ServiceResponse<List<MediaServiceInner>> response) {
                  PageImpl<MediaServiceInner> page = new PageImpl<>();
                  page.setItems(response.body());
                  return page;
              }
          });
      }
docs: Lists all of the Media Services in a resource group.
  
  @param resourceGroupName Name of the resource group within the Azure subscription.
  @return the observable to the List&lt;MediaServiceInner&gt; object