docs: public Observable<Void> deleteFaceAsync(String personGroupId, UUID personId, UUID persistedFaceId) {
          return deleteFaceWithServiceResponseAsync(personGroupId, personId, persistedFaceId).map(new Func1<ServiceResponse<Void>, Void>() {
              @Override
              public Void call(ServiceResponse<Void> response) {
                  return response.body();
              }
          });
      }