public function parse(Document $document, FeedInterface $feed) : FeedInterface
    {
        if (!$this->standard->canHandle($document)) {
            throw new UnsupportedFormatException('this is not a supported format');
        }

        $this->checkBodyStructure($document, $this->standard->getMandatoryFields());
        $this->parseContent($document, $feed);

        return $feed;
    }