code: public Observable<Object> getMetadataAsync(String appId) {
          return getMetadataWithServiceResponseAsync(appId).map(new Func1<ServiceResponse<Object>, Object>() {
              @Override
              public Object call(ServiceResponse<Object> response) {
                  return response.body();
              }
          });
      }
docs: Retrieve metric metatadata.
  Gets metadata describing the available metrics.
  
  @param appId ID of the application. This is Application ID from the API Access settings blade in the Azure portal.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the Object object