public static function multiple_remove_from_group($username, $courses)
 {
     global $CFG, $DB;
     $params = self::validate_parameters(self::multiple_remove_from_group_parameters(), array('username' => $username, 'courses' => $courses));
     $auth = new auth_plugin_joomdle();
     $id = $auth->multiple_remove_from_group($username, $courses);
     return $id;
 }