public static function fetch_course_category($courseid) {
        if (empty($courseid)) {
            debugging('Missing course id!');
            return false;
        }

        // course category has no parent
        if ($course_category = grade_category::fetch(array('courseid'=>$courseid, 'parent'=>null))) {
            return $course_category;
        }

        // create a new one
        $course_category = new grade_category();
        $course_category->insert_course_category($courseid);

        return $course_category;
    }