public function is_discussion_time_locked(discussion_entity $discussion) : bool {
        if (!$this->has_lock_discussions_after()) {
            return false;
        }

        if ($this->get_type() === 'single') {
            // It does not make sense to lock a single discussion forum.
            return false;
        }

        return (($discussion->get_time_modified() + $this->get_lock_discussions_after()) < time());
    }