src/vs/base/browser/ui/tree/asyncDataTree.ts/AsyncDataTree/getDataNode
class AsyncDataTree:	private getDataNode(element: TInput | T): IAsyncDataTreeNode<TInput, T> {
		const node: IAsyncDataTreeNode<TInput, T> | undefined = this.nodes.get((element === this.root.element ? null : element) as T);

		if (!node) {
			throw new TreeError(this.user, `Data tree node not found: ${element}`);
		}

		return node;
	}