docs: protected static void quickSort(Instances insts, int[] indices, int attidx, int left, int right) {
  
      if (left < right) {
        int middle = partition(insts, indices, attidx, left, right);
        quickSort(insts, indices, attidx, left, middle);
        quickSort(insts, indices, attidx, middle + 1, right);
      }
    }