src/vs/workbench/contrib/notebook/browser/notebookServiceImpl.ts/NotebookService/withNotebookDataProvider
class NotebookService:	async withNotebookDataProvider(viewType: string): Promise<ComplexNotebookProviderInfo | SimpleNotebookProviderInfo> {
		const selected = this.notebookProviderInfoStore.get(viewType);
		if (!selected) {
			throw new Error(`UNKNOWN notebook type '${viewType}'`);
		}
		await this.canResolve(selected.id);
		const result = this._notebookProviders.get(selected.id);
		if (!result) {
			throw new Error(`NO provider registered for view type: '${selected.id}'`);
		}
		return result;
	}