The namespace for the attribute. This will usually be GUMBO_ATTR_NAMESPACE_NONE, but some XLink/XMLNS/XML attributes take special values, per: http://www.whatwg.org/specs/web-apps/current-work/multipage/tree-construction.html#adjust-foreign-attributes
See Implementation
The namespace for the attribute. This will usually be GUMBO_ATTR_NAMESPACE_NONE, but some XLink/XMLNS/XML attributes take special values, per: http://www.whatwg.org/specs/web-apps/current-work/multipage/tree-construction.html#adjust-foreign-attributes