list property
List of Items should be non Empty and you must map your
List<T> to List<AlphaModel>
e.g
List<UserModel> _list;
_list.map((user)=>AlphaModel(user.name)).toList();
where each item of this list
will be mapped to
each widget returned by ItemBuilder to uniquely identify
that widget.
Implementation
final List<AlphaModel> list;