Ionic native map

Hello,
I’m trying to use the ionic Native Map in my App.
here is my code:
`this.platform.ready().then(() => {
this.map = new GoogleMap(‘article-details-map’);

  GoogleMap.isAvailable().then(() => {

    this.map.one(GoogleMapsEvent.MAP_READY).subscribe((data) =>{
      console.log('Map is ready!');
      alert("GoogleMap.onMapReady(): " + JSON.stringify(data));
    });
  });

});`

I have test the code on a real device and with the Chrome inspector i get this error

EXCEPTION: Error: Uncaught (in promise): TypeError: _this.map.one(…).subscribe is not a function

it’s on() instead of one()