public function fetchRequestToken(&$request)
    {
        $this->getVersion($request);
        
        $consumer = $this->getConsumer($request);
        
        // no token required for the initial token request
        $token = null;
        
        $this->checkSignature($request, $consumer, $token);
        
        // Rev A change
        $callback = $request->getParameter('oauth_callback');
        $new_token = $this->data_store->newRequestToken($consumer, $callback);
        
        return $new_token;
    }