src/vs/base/browser/ui/tree/indexTreeModel.ts/IndexTreeModel/constructor
class IndexTreeModel:	constructor(
		private user: string,
		private list: IList<ITreeNode<T, TFilterData>>,
		rootElement: T,
		options: IIndexTreeModelOptions<T, TFilterData> = {}
	) {
		this.collapseByDefault = typeof options.collapseByDefault === 'undefined' ? false : options.collapseByDefault;
		this.filter = options.filter;
		this.autoExpandSingleChildren = typeof options.autoExpandSingleChildren === 'undefined' ? false : options.autoExpandSingleChildren;

		this.root = {
			parent: undefined,
			element: rootElement,
			children: [],
			depth: 0,
			visibleChildrenCount: 0,
			visibleChildIndex: -1,
			collapsible: false,
			collapsed: false,
			renderNodeCount: 0,
			visibility: TreeVisibility.Visible,
			visible: true,
			filterData: undefined
		};
	}