Is it possible to test for a super user?

Something like...

{{ if logged_in }}
    {{ if isSuper }}
        <li><a href="{{ link to='invoices' }}">Invoices</a></li>
    {{ /if }}    
        <li><a href="{{ link to='users' }}">Users</a></li>
        <li><a href="{{ user:logout_url }}">Log out</a></li>
{{ else }}
    <li><a href="{{ link to='login' }}">Log in</a></li>
    <li><a href="{{ link to='register' }}">Register</a></li>
{{ /if }}