public function pushNotification(PushNotification $notification, PushSubscription $subscription, int $ttl = 3600) : ResponseInterface
    {
        return $this->pushNotificationAsync($notification, $subscription, $ttl)->wait();
    }
public function pushNotification(PushNotification $notification, PushSubscription $subscription, int $ttl = 3600) : ResponseInterface
    {
        return $this->pushNotificationAsync($notification, $subscription, $ttl)->wait();
    }
public function pushNotification ( PushNotification $ notification , PushSubscription $ subscription , int $ ttl = 3600 ) : ResponseInterface { return $ this -> pushNotificationAsync ( $ notification , $ subscription , $ ttl ) -> wait ( ) ; }
Send a push notification.

@param PushNotification $notification
@param PushSubscription $subscription
@param int $ttl

@return ResponseInterface
Send a push notification .