Pimcore\Model\Document\Link::__sleep PHP Method

    public function __sleep()
    {
        $finalVars = [];
        $parentVars = parent::__sleep();
        $blockedVars = ["object"];
        foreach ($parentVars as $key) {
            if (!in_array($key, $blockedVars)) {
                $finalVars[] = $key;
            }
        }
        return $finalVars;
    }