src/vs/workbench/contrib/notebook/common/model/notebookTextModel.ts/NotebookTextModel/dispose
class NotebookTextModel:	override dispose() {
		if (this._isDisposed) {
			// NotebookEditorModel can be disposed twice, don't fire onWillDispose again
			return;
		}

		this._isDisposed = true;
		this._onWillDispose.fire();
		this._undoService.removeElements(this.uri);

		dispose(this._cellListeners.values());
		this._cellListeners.clear();

		dispose(this._cells);
		this._cells = [];
		super.dispose();
	}