public function get_unsubscribediscussionlink() {
        if (!\mod_forum\subscriptions::is_subscribable($this->forum)) {
            return null;
        }
        $link = new \moodle_url(
            '/mod/forum/subscribe.php', array(
                'id'  => $this->forum->id,
                'd'   => $this->discussion->id,
            )
        );

        return $link->out(false);
    }