groupRectanglesAsync function
Implementation
Future<VecRect> groupRectanglesAsync(VecRect rects, int groupThreshold, double eps) async {
  return cvRunAsync0((callback) => cobjdetect.cv_groupRectangles(rects.ptr, groupThreshold, eps, callback), (
    c,
  ) {
    return c.complete(rects);
  });
}