public function detachFromDepartment($id = null, $identifier = null, $username = null, $department_id = null, $code = null)
    {
        $fields = [];

        if (!is_null($id)) $fields['id'] = $id;
        if (!is_null($identifier)) $fields['identifier'] = $identifier;
        if (!is_null($username)) $fields['username'] = $username;
        if (!is_null($department_id)) $fields['department_id'] = $department_id;
        if (!is_null($code)) $fields['code'] = $code;

        return $this->_del($fields, 'department');
    }