what about something like...

``template``
  Attribute.  String value.  Must be overridden.  A mako template location.  
  The default implementation of `render_content` in the base class 
  (`DebugToolbar`) will attempt to render `self.template`.  If `template` is not
  defined, and `render_content` is not overridden, a ``NotImplemented`` 
  exception will be raised.