[xwiki-users] Method that returns list of groups for a page

Hey all, I am trying to find a method that can return a list of groups that have a given access right to a given page. Is there a method(s) that allow me to do that? I'm aware that you can create an object of AccessRights onto a given page and filter in groups and users that have access rights to a given page, but only admins can see that. I need to generate a list of groups that have granted access so that when an unregistered user tries to log onto a page that he doesn't have access to, a list will be generated so that he can ask for membership to those groups. Thank you, Felix Wu