isSelectedIn method
Whether this choice is currently selected within selectedChoice.
Mirrors the original _isSelected predicate from
StandardMultiSelectField, comparing by Choice.key.
Implementation
bool isSelectedIn(List<Choice<T>> selectedChoice) {
if (isGroupingTitle) return false;
return selectedChoice
.where(
(element) => (key != null || key!.isNotEmpty) && element.key == key,
)
.isNotEmpty;
}