static L<PtBuffer> g22_allBorderTraces_withDiagonals(IImageRegion region) {
  RegionBorder_innerPoints_withDiagonals walker = new(region);
  new L<PtBuffer> out;
  walker.onNewTrace(hole -> out.add(new PtBuffer));
  walker.onFoundPoint(p -> last(out).add(p));
  walker.run();
  ret out;
}

Began life as a copy of #1034971