src/vs/workbench/contrib/notebook/browser/notebookEditorWidget.ts/NotebookEditorWidget/activeCodeEditor
class NotebookEditorWidget:	get activeCodeEditor(): IEditor | undefined {
		if (this._isDisposed) {
			return;
		}

		const [focused] = this._list.getFocusedElements();
		return this._renderedEditors.get(focused);
	}