[Ionic 4] Toggle button ativar e desativar notificações

this.platform.ready().then(() => {
    this.oneSignal.startInit(this.signal_app_id, this.firebase_id);
    this.oneSignal.inFocusDisplaying(this.oneSignal.OSInFocusDisplayOption.InAppAlert);
    this.oneSignal.handleNotificationReceived().subscribe((res) => {
      // do something when notification is received
      console.log(res);
    });
    this.oneSignal.handleNotificationOpened().subscribe((res) => {
      // do something when a notification is opened
      console.log(res);
    });
    this.oneSignal.endInit();
  });