<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def authenticate_redirect( self, callback_uri: str = None, ax_attrs: List[str] = ["name", "email", "language", "username"], ) -> None: """Redirects to the authentication URL for this service. After authentication, the service will redirect back to the given callback URI with additional parameters including ``openid.mode``. We request the given attributes for the authenticated user by default (name, email, language, and username). If you don't need all those attributes for your app, you can request fewer with the ax_attrs keyword argument. .. versionchanged:: 6.0 The ``callback`` argument was removed and this method no longer returns an awaitable object. It is now an ordinary synchronous function. """

        handler = cast(RequestHandler, self)
        callback_uri = callback_uri or handler.request.uri
        assert callback_uri is not None
        args = self._openid_args(callback_uri, ax_attrs=ax_attrs)
        endpoint = self._OPENID_ENDPOINT  # type: ignore
        handler.redirect(endpoint + "?" + urllib.parse.urlencode(args))