src/vs/workbench/contrib/notebook/browser/notebookEditorWidget.ts/NotebookEditorWidget/getEditorMemento
class NotebookEditorWidget:	protected getEditorMemento<T>(editorGroupService: IEditorGroupsService, key: string, limit: number = 10): IEditorMemento<T> {
		const mementoKey = `${NOTEBOOK_EDITOR_ID}${key}`;

		let editorMemento = NotebookEditorWidget.EDITOR_MEMENTOS.get(mementoKey);
		if (!editorMemento) {
			editorMemento = new EditorMemento(NOTEBOOK_EDITOR_ID, key, this.getMemento(StorageScope.WORKSPACE), limit, editorGroupService);
			NotebookEditorWidget.EDITOR_MEMENTOS.set(mementoKey, editorMemento);
		}

		return editorMemento as IEditorMemento<T>;
	}