1. DomName('XPathNSResolver.lookupNamespaceURI')
  2. DocsEditable()
String lookupNamespaceUri(String prefix)

Source 

@DomName('XPathNSResolver.lookupNamespaceURI')
@DocsEditable()
String lookupNamespaceUri(String prefix) => _blink.BlinkXPathNSResolver.instance.lookupNamespaceURI_Callback_1_(this, prefix);