ReactiveNetwork.observeNetworkConnectivity

Question

I am using ReactiveNetwork to observe my wifi. I added a callback that when the wifi gets disconnected, an alert dialog pops up. However, the dialog gets pop up when wifi is turned off while the app is not shown (home). I want to unsubscribe but I can't find the correct way to do the corresponding unsubscribe for this method. How do I unsubscribe?

ReactiveNetwork.observeNetworkConnectivity(context)
                .subscribeOn(Schedulers.io())
                .filter(ConnectivityPredicate.hasType(ConnectivityManager.TYPE_WIFI))
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Consumer<Connectivity>() {
                    @Override 
                    public void accept(final Connectivity connectivity) {
                        if(connectivity.isAvailable()) {
                            callback.onWifiConnected();
                        }
                        else {
                            callback.onWifiDisconnected();
                        }
                    }
                });