protected function _toOptionArray($valueField = 'job_code', $labelField = 'name', $additional = array())
    {
        $options = array();

        $additional['value'] = $valueField;
        $additional['label'] = $labelField;

        foreach ($this as $item) {
            /** @var Aoe_Scheduler_Model_Job $item */
            $data = array();
            foreach ($additional as $code => $field) {
                $data[$code] = $item->getDataUsingMethod($field);
            }
            $options[] = $data;
        }
        return $options;
    }