public function __construct($content, HtmlConverterInterface $htmlConverter = null)
{
if (!$this->hasXmlDeclaration($content)) {
$content = $this->addXmlDeclaration($content);
}
if (!$this->hasDoctypeDeclaration($content)) {
$content = $this->addDoctypeDeclaration($content);
}
$this->content = $content;
$this->htmlConverter = $htmlConverter;
}