Jose\KeyConverter\ECKey::isPKCS8 PHP Method

    private function isPKCS8(array $children)
    {
        if (3 !== count($children)) {
            return false;
        }
        $classes = [0 => Integer::class, 1 => Sequence::class, 2 => OctetString::class];
        foreach ($classes as $k => $class) {
            if (!$children[$k] instanceof $class) {
                return false;
            }
        }
        return true;
    }