lookup method
Looks up which proxy to use to connect to uri.
'direct://' is returned when no proxy is needed.
Implementation
Future<List<String>> lookup(String uri) async {
var result = await _object.callMethod(
'org.freedesktop.portal.ProxyResolver', 'Lookup', [DBusString(uri)],
replySignature: DBusSignature('as'));
return result.returnValues[0].asStringArray().toList();
}