src/vs/workbench/contrib/notebook/common/model/notebookTextModel.ts/StackOperation/undo
class StackOperation:	async undo(): Promise<void> {
		this._pauseableEmitter.pause();
		for (let i = this._operations.length - 1; i >= 0; i--) {
			await this._operations[i].undo();
		}
		this._postUndoRedo(this._beginAlternativeVersionId);
		this._pauseableEmitter.fire({
			rawEvents: [],
			synchronous: undefined,
			versionId: this.textModel.versionId,
			endSelectionState: this._beginSelectionState
		});
		this._pauseableEmitter.resume();
	}