Reply To: bbpress template tags in wp

I had used the code (below) prior to posting here in the forum and it didn’t work for me…

bbp_list_forums(array('before' =>'<ul>','after'=>'</ul>','link_before'=>'<li>','link_after'=>'</li>','count_before'=>'(','count_after'=>')','count_sep'=>',','separator'=>',','forum_id'=>'','show_topic_count'=>true,'show_reply_count'=>true,));

and it outputs nothing… what am I doing wrong? I put this in my header.php file in my wordpress theme directory.