protected function convertKeys(array $meta) {
        $return = [];
        foreach ($meta as $key => $value) {
            if (is_array($value)) {
                $value = $this->convertKeys($value);
            }
            $newKey = strtolower($key);
            $newKey = preg_replace('/[^\w+]/', '_', $newKey);
            $return[$newKey] = $value;
        }
        return $return;
    }