public function addUniversalTransferDocumentSellerTitles(\AgentSIB\Diadoc\Api\Proto\Events\XmlDocumentAttachment $value)
    {
        if ($this->UniversalTransferDocumentSellerTitles === null) {
            $this->UniversalTransferDocumentSellerTitles = new \Protobuf\MessageCollection();
        }

        $this->UniversalTransferDocumentSellerTitles->add($value);
    }