Function parse_ns_str 

pub fn parse_ns_str(input: &str) -> Result<Document, XmlError>

Parse input with XML Namespaces 1.0 processing enabled — resolves xmlns declarations, fills the namespace field on every element and prefixed attribute, validates QName syntax, and rejects undeclared prefixes. Convenience wrapper over parse_str with namespace_aware: true.

Arena-DOM equivalent of parse_ns_str.