code: public Observable<List<FaceList>> listAsync() {
          return listWithServiceResponseAsync().map(new Func1<ServiceResponse<List<FaceList>>, List<FaceList>>() {
              @Override
              public List<FaceList> call(ServiceResponse<List<FaceList>> response) {
                  return response.body();
              }
          });
      }
docs: Retrieve information about all existing face lists. Only faceListId, name and userData will be returned.
  
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the List&lt;FaceList&gt; object