protected function get_manage_subscriptions_button() {
        if (calendar_user_can_add_event($this->calendar->course)) {
            $managesubscriptionurl = new moodle_url('/calendar/managesubscriptions.php', $this->get_link_params());
            return new \single_button($managesubscriptionurl,
                    get_string('managesubscriptions', 'calendar'), 'get');
        }
    }