protected function normalizeData($rawData)
    {
        $data = array();
        foreach ($rawData as $key => $value) {
            if (is_array($value)) {
                $item = array('text' => $key, 'children' => $this->normalizeData($rawData[$key]));
            } else {
                $item = array('id' => $key, 'text' => $value);
            }
            $data[] = $item;
        }
        return $data;
    }