That is a HTML generator library.

And as I've said, for HTML5 compliance you need to also parse JavaScript, see second sentence here https://dev.w3.org/html5/spec-LC/parsing.html#overview-of-th...

A good first smoke-test for HTML5 supporting parsers is the following html fragment

   <input disabled>

XML-like parsers (masquerading as having "HTML5 support") will fail if tags aren't closed or self-closing, and if there are attributes without an explicit value.