code: public Observable<ExpressRoutePortInner> getByResourceGroupAsync(String resourceGroupName, String expressRoutePortName) {
          return getByResourceGroupWithServiceResponseAsync(resourceGroupName, expressRoutePortName).map(new Func1<ServiceResponse<ExpressRoutePortInner>, ExpressRoutePortInner>() {
              @Override
              public ExpressRoutePortInner call(ServiceResponse<ExpressRoutePortInner> response) {
                  return response.body();
              }
          });
      }
docs: Retrieves the requested ExpressRoutePort resource.
  
  @param resourceGroupName The name of the resource group.
  @param expressRoutePortName The name of ExpressRoutePort.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the ExpressRoutePortInner object