Function codepoints_to_string 

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

fn:codepoints-to-string($arg as xs:integer*) as xs:string

Converts a sequence of codepoints to a string. Accepts any numeric type that can be converted to an integer codepoint.