srecord noeq CountHolesInRegion(IImageRegion region) {
  int holes;
  
  int get() {
    if (region == null) ret 0;
    var borderWalker = new RegionBorder_innerPoints_v2(region);
    borderWalker.onNewTrace(isHole -> { if (isHole) holes++; });
    borderWalker.run();
    ret holes;
  }
}