Pimcore\Model\Document\PageSnippet::setContentMasterDocument PHP Method

    public function setContentMasterDocument($document)
    {
        if ($document instanceof Document\PageSnippet) {
            $this->setContentMasterDocumentId($document->getId());
        } else {
            $this->setContentMasterDocumentId(null);
        }
        return $this;
    }