src/vs/workbench/api/browser/mainThreadTreeViews.ts/TreeViewDataProvider/postGetChildren
class TreeViewDataProvider:	private async postGetChildren(elements: ITreeItem[] | undefined): Promise<ResolvableTreeItem[] | undefined> {
		if (elements === undefined) {
			return undefined;
		}
		const result: ResolvableTreeItem[] = [];
		const hasResolve = await this.hasResolve;
		if (elements) {
			for (const element of elements) {
				const resolvable = new ResolvableTreeItem(element, hasResolve ? (token) => {
					return this._proxy.$resolve(this.treeViewId, element.handle, token);
				} : undefined);
				this.itemsMap.set(element.handle, resolvable);
				result.push(resolvable);
			}
		}
		return result;
	}