@Override
 public void endTree(Node left, Node right) {
   if (intersects(left, right)) {
     super.endTree(left, right);
   }
   tracker.endTree(left, right);
 }
 @Override
 public void feature(Node left, Node right) {
   if (intersects(left, right)) {
     super.feature(left, right);
   }
 }
 @Override
 public void endBucket(int bucketIndex, int bucketDepth, Bucket left, Bucket right) {
   if (intersects(left, right)) {
     super.endBucket(bucketIndex, bucketDepth, left, right);
   }
 }