src/vs/workbench/api/common/extHostTypes.ts/TreeItem/constructor
class TreeItem:	constructor(arg1: string | vscode.TreeItemLabel | URI, public collapsibleState: vscode.TreeItemCollapsibleState = TreeItemCollapsibleState.None) {
		if (URI.isUri(arg1)) {
			this.resourceUri = arg1;
		} else {
			this.label = arg1;
		}
	}