private function prepareHtmlForDomConversion($html)
    {
        $htmlWithSelfClosingSlashes = $this->ensurePhpUnrecognizedSelfClosingTagsAreXml($html);
        $htmlWithDocumentType = $this->ensureDocumentType($htmlWithSelfClosingSlashes);

        return $this->addContentTypeMetaTag($htmlWithDocumentType);
    }