* @param string $order_by the field to order the users by. Valid values are 'lastname', 'firstname', 'username', 'email', 'official_code' OR a part of a SQL statement that starts with ORDER BY ...
* @return array
*/
public static function get_user_list_from_course_code($course_code, $with_session = true, $session_id = 0, $limit = '', $order_by = '') {
public static function get_user_list_from_course_code($course_code, $session_id = 0, $limit = '', $order_by = '') {