How to use the @ionic-native/google-maps.GoogleMapsEvent.MARKER_CLICK function in @ionic-native/google-maps

.then(marker => {
            marker.on(GoogleMapsEvent.MARKER_CLICK)
              .subscribe(() => {
                alert('clicked');
              });
          });

tilt: 30
       }
    };

    this.map = GoogleMaps.create('map', mapOptions);

    let marker: Marker = this.map.addMarkerSync({
      title: 'Ionic',
      icon: 'blue',
      animation: 'DROP',
      position: {
        lat: 13.0380523,
        lng: 80.21371
      }
    });
    marker.on(GoogleMapsEvent.MARKER_CLICK).subscribe(() => {
      alert('clicked');
    });
  }
}