public function getPrefix(string $prefix, string $className): string
    {
        // the  prefix of annotation is exist
        if (! empty($prefix)) {
            return $prefix;
        }

        // the prefix of annotation is empty
        $reg = '/^.*\\\(\w+)' . $this->suffix . '$/';
        $prefix = '';

        if ($result = preg_match($reg, $className, $match)) {
            $prefix = lcfirst($match[1]);
        }

        return $prefix;
    }