in src/app/map/map.component.ts [111:115]
constructor(private _ngZone: NgZone, iterableDiffers: IterableDiffers) {
this._iterableDiffer = iterableDiffers.find([]).create(null);
this.pendingStyles = fetch('assets/basemap.json', { credentials: 'include' })
.then((response) => response.json());
}