Pimcore\Model\Document\Hardlink::resolveDependencies PHP Method

    public function resolveDependencies()
    {
        $dependencies = parent::resolveDependencies();
        if ($this->getSourceDocument() instanceof Document) {
            $key = "document_" . $this->getSourceDocument()->getId();
            $dependencies[$key] = ["id" => $this->getSourceDocument()->getId(), "type" => "document"];
        }
        return $dependencies;
    }