src/vs/workbench/api/common/extHostTreeViews.ts/ExtHostTreeView/resolveParent
class ExtHostTreeView:	private resolveParent(element: T): Promise<T | Root> {
		const node = this.nodes.get(element);
		if (node) {
			return Promise.resolve(node.parent ? this.elements.get(node.parent.item.handle) : undefined);
		}
		return asPromise(() => this.dataProvider.getParent!(element));
	}