src/vs/workbench/contrib/notebook/browser/services/notebookServiceImpl.ts/NotebookService/getNotebookProviderResourceRoots
class NotebookService:	getNotebookProviderResourceRoots(): URI[] {
		const ret: URI[] = [];
		this._notebookProviders.forEach(val => {
			if (val.extensionData.location) {
				ret.push(URI.revive(val.extensionData.location));
			}
		});

		return ret;
	}