How to use the @here/harp-geoutils.webMercatorTilingScheme.getTileKey function in @here/harp-geoutils

async function dumpTile(geoPoint: GeoCoordinates, level: number) {
    const tileKey = webMercatorTilingScheme.getTileKey(geoPoint, level);

    if (!tileKey) {
        throw new Error("failed to get tile");
    }

    geometryList = {};
    const buffer = (await dataProvider.getTile(tileKey)) as ArrayBuffer;
    const decoder = new Decoder();
    const adapter = new OmvProtobufDataAdapter(decoder);

    adapter.process(buffer, tileKey);
}