public function is_enabled() {
        if ($this->enabledcache === null) {
            $gradingmanager = get_grading_manager($this->assignment->get_context(), 'mod_assign', 'submissions');
            $controller = $gradingmanager->get_active_controller();
            $active = !empty($controller);

            if ($active) {
                $this->enabledcache = false;
            } else {
                $this->enabledcache = parent::is_enabled();
            }
        }
        return $this->enabledcache;
    }