human
Solve the following python programming problem given the following code:
def PollForAuthentication(self, callback) : 
    'Poll the google authorization service to find if the user code generated
    in a previous call to GetUserCode() has been used to authorize a google user account.
    If an account has been authorized, this method will use that authorization to log
    into the viewfinder service, thus retrieving the needed authentication cookie.

    The given callback will be invoked with a boolean parameter to indicate whether
    or not the authentication was successful.  If authentication was not successful, then
    this method can be polled again until it is successful.
    ' 
    if (not hasattr (self, '_device_code')) : 
        raise ScenarioLoginError ('Must call GetUserCode() on a device before using the PollForAuthentication() method.') 
http_client = httpclient.AsyncHTTPClient () 
    def _OnLogin(response) : 
        if (not (response.code in (200, 302))) : 
            raise ScenarioLoginError (('Error during login process:%s' % response.error)) 
self._user_cookie = self._GetUserCookieFromResponse (response) 
        self._SaveAuthentication () 
        callback (True) 
def _OnPollTokenEndpoint(response) : 
        json_response = www_util.ParseJSONResponse (response) 
        if ('error' in json_response) : 
            callback (False) 
else : 
            refresh_token = json_response.get ('refresh_token') 
            url = ('https://%s:%d/auth/google?refresh_token=%s' % (ServerEnvironment.GetHost (), options.options.port, refresh_token)) 
            http_client.fetch (url, method = 'POST', callback = _OnLogin, body = json.dumps ({ 
                
}), validate_cert = False, follow_redirects = False, headers = { 
                'Content-Type' : 'application/json', 
}) 
url = _GOOGLE_OAUTH2_TOKEN_URL 
    request_args = { 
        'client_id' : secrets.GetSecret ('google_client_mobile_id'), 
        'client_secret' : secrets.GetSecret ('google_client_mobile_secret'), 
        'code' : self._device_code, 
        'grant_type' :...
    
    Given the code above, what is a proper replacement for <MASK>? Choose among: callback, _OnLogin, url, self, request_args, http_client
assistant
#Here is Python code to find if the user code generated
.
def _OnPollTokenEndpoint(