src/vs/base/browser/ui/tree/objectTreeModel.ts/ObjectTreeModel/getParentNodeLocation
class ObjectTreeModel:	getParentNodeLocation(element: T | null): T | null {
		if (element === null) {
			throw new TreeError(this.user, `Invalid getParentNodeLocation call`);
		}

		const node = this.nodes.get(element);

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

		const location = this.model.getNodeLocation(node);
		const parentLocation = this.model.getParentNodeLocation(location);
		const parent = this.model.getNode(parentLocation);

		return parent.element;
	}