code: public Observable<PersistedFace> addFaceFromStreamAsync(String faceListId, byte[] image, AddFaceFromStreamOptionalParameter addFaceFromStreamOptionalParameter) {
          return addFaceFromStreamWithServiceResponseAsync(faceListId, image, addFaceFromStreamOptionalParameter).map(new Func1<ServiceResponse<PersistedFace>, PersistedFace>() {
              @Override
              public PersistedFace call(ServiceResponse<PersistedFace> response) {
                  return response.body();
              }
          });
      }
docs: Add a face to a face list. The input face is specified as an image with a targetFace rectangle. It returns a persistedFaceId representing the added face, and persistedFaceId will not expire.
  
  @param faceListId Id referencing a particular face list.
  @param image An image stream.
  @param addFaceFromStreamOptionalParameter the object representing the optional parameters to be set before calling this API
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the PersistedFace object