expand property

bool get expand

@override
bool get expand => _expand?.get() ?? false;

set expand (dynamic v)

@override
set expand(dynamic v) {
  if (_expand != null) {
    _expand!.set(v);
  } else if (v != null) {
    _expand = BooleanObservable(Binding.toKey(id, 'expand'), v,
        scope: scope, listener: onPropertyChange);
  }
}