setDocumentMediaFileId example

$documentStruct = $this->documentGenerator->generate(
            $documentType->getTechnicalName(),
            [$document->getOrderId() => $operation],
            $context
        )->getSuccess()->first();

        if ($documentStruct === null) {
            return null;
        }

        $documentMediaId = $documentStruct->getMediaId();
        $document->setDocumentMediaFileId($documentMediaId);

        return $documentMediaId;
    }
}