src/vs/base/browser/ui/tree/compressedObjectTreeModel.ts/CompressibleObjectTreeModel/onDidChangeCollapseState
class CompressibleObjectTreeModel:	get onDidChangeCollapseState(): Event<ICollapseStateChangeEvent<T | null, TFilterData>> {
		return Event.map(this.model.onDidChangeCollapseState, ({ node, deep }) => ({
			node: this.nodeMapper.map(node),
			deep
		}));
	}