src/vs/workbench/contrib/notebook/common/model/notebookTextModel.ts/NotebookTextModel/_getDefaultCollapseState
class NotebookTextModel:	private _getDefaultCollapseState(cellDto: ICellDto2): NotebookCellCollapseState | undefined {
		const defaultConfig = cellDto.cellKind === CellKind.Code ? this._defaultCollapseConfig?.codeCell : this._defaultCollapseConfig?.markupCell;
		return cellDto.collapseState ?? (defaultConfig ?? undefined);
	}