public static function isFile($object, $value): bool
    {
        // allow empty fields, "required" option filter that
        if ($object === null) {
            return true;
        }

        $all = false;
        // if string is given
        if (!Any::isArray($value)) {
            if ($value === '*') {
                $all = true;
            } else {
                $value = [$value];
            }
        }

        // input file is not object?
        if ($object === null || !Any::isObj($object)) {
            return false;
        }

        // get guess file type, based on mime-type
        $type = $object->guessExtension();
        if ($type === null) {
            return false;
        }

        return ($all ? true : Arr::in($type, $value));
    }