docs: @Override
  	public void clear() {
  		if (this.left != null) {
  			final N child = this.left;
  			setLeftChild(null);
  			child.clear();
  		}
  		if (this.right != null) {
  			final N child = this.right;
  			setRightChild(null);
  			child.clear();
  		}
  		removeAllUserData();
  	}