docs: function getRoot(i, list) {
  	for (var x = list.height; x > 0; x--) {
  		var slot = i >> x * _const.B;
  		while (list.sizes[slot] <= i) {
  			slot++;
  		}
  		if (slot > 0) {
  			i -= list.sizes[slot - 1];
  		}
  		list = list[slot];
  	}
  	return list[i];
  }