Render the link for the tab-pane. It must be called after render so css_class is updated
        with active if needed.

def render_link(self, template_pack=TEMPLATE_PACK, **kwargs):
        """
        Render the link for the tab-pane. It must be called after render so css_class is updated
        with active if needed.
        """
        link_template = self.link_template % template_pack
        return render_to_string(link_template, {'link': self})