docs: private static int[] toIntArray(List<Integer> list) {
      if (list == null || list.isEmpty()) {
        return NO_BINDS;
      }
      int[] res = new int[list.size()];
      for (int i = 0; i < list.size(); i++) {
        res[i] = list.get(i); // must not be null
      }
      return res;
    }