function is_tree (from docs: “Conditional Tags”)

Hi!

I was reading the doc about conditional tags and decided to add the is_tree() function to my theme. So, as proposed, I added the snippet 4 to my themes functions.php.

Looks like:

<?php

if ( function_exists('register_sidebars') )
        register_sidebars(2);
?>
function is_tree($pid) {      // $pid = The ID of the page we're looking for pages underneath
	global $post;         // load details about this page
	if(is_page()&&($post->post_parent==$pid||is_page($pid)))
               return true;   // we're at the page or at a sub page
	else
               return false;  // we're elsewhere
};

But now on the top of my page I see the text of the added function.
Seems like I added just a textparagraph. Am I missing something?
Anyone who can explain to me how to add this function properly to my functions.php?

any help appreciated,
cya, piedro