TypeError: Cannot read property 'extend' of undefined

I am using aurelia framework. Earlier i was using Leaflet Mapbox Tile layer library to display vector tiles but now i want to use a seperate tile server to render vector tiles. For this i planned to use Leaflet VectorGrid library. I installed the package using "jspm install github:Leaflet/Leaflet.VectorGrid" and also installed leaflet 1.0.0 version. I am importing this like import 'Leaflet/Leaflet.VectorGrid';
But when i am trying to call vectorGrid.protobuf i am getting error as "Cannot read property 'protobuf' of undefined".Seems vectorGrid instance is not being created.See the screenshot.

My import sequence is :

import * as D from "leaflet-draw";
import * as L from "leaflet";
import 'Leaflet/Leaflet.VectorGrid';

Code line :
L.vectorGrid.protobuf(mapboxUrl, mapboxVectorTileOptions);

Please help me where i am doing wrong ?

Start by reproducing the Aurelia/JSPM setup using the shown import sequence for leaflet, leaflet-draw, and Leaflet.VectorGrid. Check the Leaflet.VectorGrid entry point and the L.vectorGrid.protobuf call to determine why vectorGrid is undefined; the issue is done when that call is available and no longer raises the TypeError.