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