src/vs/workbench/contrib/notebook/common/notebookEditorModel.ts/NotebookFileWorkingCopyModel/constructor
class NotebookFileWorkingCopyModel:	constructor(
		private readonly _notebookModel: NotebookTextModel,
		private readonly _notebookSerializer: INotebookSerializer
	) {
		this.onWillDispose = _notebookModel.onWillDispose.bind(_notebookModel);

		this._changeListener = _notebookModel.onDidChangeContent(e => {
			for (const rawEvent of e.rawEvents) {
				if (rawEvent.kind === NotebookCellsChangeType.Initialize) {
					continue;
				}
				if (rawEvent.transient) {
					continue;
				}
				this._onDidChangeContent.fire({
					isRedoing: false, //todo@rebornix forward this information from notebook model
					isUndoing: false,
					isInitial: false, //_notebookModel.cells.length === 0 // todo@jrieken non transient metadata?
				});
				break;
			}
		});
	}