Sulu\Bundle\ContentBundle\Document\PageDocument::setParent PHP Method

    public function setParent($parent)
    {
        $this->parent = $parent;
    }

 private function createPage()
 {
     $page = new PageDocument();
     $page->setTitle('Hello');
     $page->setResourceSegment('/hello');
     $page->setParent($this->contentDocument);
     $page->setStructureType('internallinks');
     $page->getStructure()->bind(['title' => 'World', 'internalLinks' => [$this->contentDocument->getUuid()]], true);
     $this->documentManager->persist($page, 'fr');
     $this->documentManager->flush();
     return $page;
 }