public static function preload_course($courseid) {
        // Users can call this multiple times without doing any harm
        if (isset(context::$cache_preloaded[$courseid])) {
            return;
        }
        $coursecontext = context_course::instance($courseid);
        $coursecontext->get_child_contexts();

        context::$cache_preloaded[$courseid] = true;
    }