protected static function get_subcontext($forum, $discussion = null, $post = null) {
        $subcontext = [];
        if (null !== $discussion) {
            $subcontext += self::get_discussion_area($discussion);

            if (null !== $post) {
                $subcontext[] = get_string('posts', 'mod_forum');
                $subcontext = array_merge($subcontext, static::get_post_area_for_parent($post));
            }
        }

        return $subcontext;

    }