How to enable black mode in Google Maps in iOS

let mapStyleUrl = Bundle.main.url(forResource: "mapStyle", withExtension: "json")!
mapView.mapStyle = try? GMSMapStyle(contentsOfFileURL: mapStyleUrl)

{
    "elementType": "geometry",
    "stylers": [
        {
            "color": "#424242"
        }
    ]
}

{
    "featureType": "water",
    "elementType": "geometry",
    "stylers": [
        {
            "color": "#2E2E2E"
        }
    ]
}