main.dart

void main() {
  Map<Calc, List<Calc>> map = {};
}

class SelectionItem {
  SelectionItem(
      {@required this.name, @required this.max, @required this.description});
  final String name;
  final int max;
  final String description;
  
  factory SelectionItem.fromMap(Map<String, dynamic> data) {
    if (data == null) {
      return null;
    }
    final String name = data['name'];
    final int max = data['max'];
    final String description = data['description'];
    return SelectionItem(name: name, max: max, description: description);
  }
  Map<String, dynamic> toMap() {
    return {
      'name': name,
      'max': max,
      'description': description,
    };
  }
}