Function normalize_space 

pub fn normalize_space<N: DomNavigator>(
    context: &mut DynamicContext<'_, N>,
    args: Vec<XPathValue<N>>,
) -> Result<XPathValue<N>, XPathError>

fn:normalize-space($arg as xs:string?) as xs:string fn:normalize-space() as xs:string (uses context item)

Normalizes whitespace in a string.