svoid test_PtTree() {
  int n = 10;
  Set<Pt> set = repFToSet(n, () -> randomPt(10));
  print(set);
  PtTree tree = PtTree.fromPointSet(set);
  //printIndentedStruct(tree);
  print(asList(iterator(tree)));
  for (var p : set) {
    Rect r = rectAround(p, 1);
    var l = tree.pointsIn(r);
    printVars(+p, +l);
    assertTrueVerbose(str(r), l.contains(p));
    for (p2 : set)
      if (!r.contains(p2))
        if (l.contains(p2))
          fail("Bad bad: " + p2);
  }
}