How to customize xtemplate.theme for nodewords?

I am trying to customize the xtemplate.theme to work with nodewords, no success
whatever I try.

In my template I have put this into the HEAD section:

meta name="keywords" content="{nodewords}"

In theme, I have put this:

 function nodewords ($nodewords) {

$nodewords = module_invoke("nodewords", "get", $nid);
$xtemplate->template->assign("nodewords", $nodewords);
$xtemplate->template->parse("nodewords");
return $nodewords;
} 

Looking at the source of the node I have assigned keywords to, the output is empty, ie. content="".

What am I doing wrong?

Using Drupal 4.4.2, the module is working, the table is neatly populated by node's data entered through administration field, but I just can't figure the way to modify the theme properly.

Would you be so kind and help me out a bit? I have tried numerous combinations, no success.

Thanks ;)