main.dart

Widget _renderSteps(List<Step> steps) {
  return ExpansionPanelList.radio(
    children: steps.map<ExpansionPanelRadio>((Step step) {
      return ExpansionPanelRadio(
        headerBuilder: (BuildContext context, bool isExpanded) {
          return ListTile(
            title: Text(step.title),
          );
        },
        body: ListTile(
          title: Text(step.body),
          subtitle: _renderSteps(step.subSteps)
        ),
        value: step.title
      );
    }).toList(),
  );
}