private function verifyMimeType($mime_type)
    {
        $allowed = $this->config['allowed_mime_types'];
        if (! empty($allowed) && ! in_array(strtolower($mime_type), $allowed)) {
            throw FileNotSupportedException::mimeRestricted(strtolower($mime_type), $allowed);
        }

        return $mime_type;
    }