src/vs/workbench/contrib/notebook/browser/controller/foldingController.ts/FoldingController/_updateEditorFoldingRanges
class FoldingController:	private _updateEditorFoldingRanges() {
		if (!this._foldingModel) {
			return;
		}

		if (!this._notebookEditor.hasModel()) {
			return;
		}

		const vm = this._notebookEditor._getViewModel() as NotebookViewModel;

		vm.updateFoldingRanges(this._foldingModel.regions);
		const hiddenRanges = vm.getHiddenRanges();
		this._notebookEditor.setHiddenAreas(hiddenRanges);
	}