docs: public static RoaringBitmap priorityqueue_xor(RoaringBitmap... bitmaps) {
      // TODO: This code could be faster, see priorityqueue_or
      if (bitmaps.length == 0) {
        return new RoaringBitmap();
      }
  
      PriorityQueue<RoaringBitmap> pq =
          new PriorityQueue<>(bitmaps.length, new Comparator<RoaringBitmap>() {
            @Override
            public int compare(RoaringBitmap a, RoaringBitmap b) {
              return (int)(a.getLongSizeInBytes() - b.getLongSizeInBytes());
            }
          });
      Collections.addAll(pq, bitmaps);
      while (pq.size() > 1) {
        RoaringBitmap x1 = pq.poll();
        RoaringBitmap x2 = pq.poll();
        pq.add(RoaringBitmap.xor(x1, x2));
      }
      return pq.poll();
    }