static RGBImageRectAndState callEyebrowFinder(F1<RGBImage, RectAndState> finder, RGBImage image) {
  ret RGBImageRectAndState(image, callF(finder, image));
}

static L<RGBImageRectAndState> callFaceFinder(final F1<RGBImage, RectAndState> finder, Iterable<RGBImage> images) {
  ret map(images, func(RGBImage image) -> RGBImageRectAndState {
    callEyebrowFinder(finder, image)
  });
}