src/vs/workbench/contrib/notebook/browser/notebookEditor.ts/NotebookEditor/_saveEditorViewState
class NotebookEditor:	private _saveEditorViewState(input: IEditorInput | undefined): void {
		if (this.group && this._widget.value && input instanceof NotebookEditorInput) {
			if (this._widget.value.isDisposed) {
				return;
			}

			const state = this._widget.value.getEditorViewState();
			this._editorMemento.saveEditorState(this.group, input.resource, state);
		}
	}