static RGBImageAndRect callFaceFinder(F1<RGBImage, Rect> finder, RGBImage image) {
  ret RGBImageAndRect(image, callF(finder, image));
}

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