private function convertValue($value)
    {
        if (empty($value)) {
            return null;
        }

        if (\is_array($value)) {
            return $value;
        }

        switch ($this->fieldType) {
            case 'radio':
                return $value;
            case 'checkbox':
                $delimiter = (false !== \stripos($value, "\t")) ? "\t" : ',';

                return StringUtil::trimsplit($delimiter, $value);
            default:
        }
        throw new \RuntimeException('Unknown field type encountered: ' . $this->fieldType);
    }