code: public Observable<Page<AppServicePlanInner>> listByResourceGroupAsync(final String resourceGroupName) {
          return listByResourceGroupWithServiceResponseAsync(resourceGroupName)
              .map(new Func1<ServiceResponse<Page<AppServicePlanInner>>, Page<AppServicePlanInner>>() {
                  @Override
                  public Page<AppServicePlanInner> call(ServiceResponse<Page<AppServicePlanInner>> response) {
                      return response.body();
                  }
              });
      }
docs: Get all App Service plans in a resource group.
  Get all App Service plans in a resource group.
  
  @param resourceGroupName Name of the resource group to which the resource belongs.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the PagedList&lt;AppServicePlanInner&gt; object