code: public Observable<Page<ContainerServiceInner>> listByResourceGroupAsync(final String resourceGroupName) {
          return listByResourceGroupWithServiceResponseAsync(resourceGroupName)
              .map(new Func1<ServiceResponse<Page<ContainerServiceInner>>, Page<ContainerServiceInner>>() {
                  @Override
                  public Page<ContainerServiceInner> call(ServiceResponse<Page<ContainerServiceInner>> response) {
                      return response.body();
                  }
              });
      }
docs: Gets a list of container services in the specified resource group.
  Gets a list of container services in the specified subscription and resource group. The operation returns properties of each container service including state, orchestrator, number of masters and agents, and FQDNs of masters and agents.
  
  @param resourceGroupName The name of the resource group.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the PagedList&lt;ContainerServiceInner&gt; object