code: @SafeVarargs
  	public final TreeNode<T> attach(final T... children) {
  		for (T child : children) {
  			attach(TreeNode.of(child));
  		}
  
  		return this;
  	}
docs: Attaches the given {@code children} to {@code this} node.
  
  @param children the children to attach to {@code this} node
  @return {@code this} tree-node, for method chaining
  @throws NullPointerException if the given {@code children} array is
  {@code null}