TypeScript / Angular import library that extends NameSpace

I am trying to use Leaflet ( https://www.npmjs.com/package/leaflet ) along with this non-npm library ( https://github.com/Sumbera/gLayers.Leaflet ) in an Angular 4 app.

I declared the namespace "L" in "Leaf" with "import" as L from "leaflet"; in my component they did cli-load-stuff and everything that works from this package.

Now the problem is that the second library (which I loaded into the Angular cli under scripts after leaflet.js) has to extend 'L' to 'L.canvasLayer', but if I name it the console says it is not and it looks like , does not exist. How can I download it? Thanks for the help!