CowGroupState constructor Null safety

1. farmershands
2. cow_group_state
3. CowGroupState
4. CowGroupState constructor

CowGroupState class

1. Constructors
2. CowGroupState
3. Properties
4. cowGroups
5. cowGroupsWithTotal
6. cowState
7. currentCowGroup
8. hashCode
9. hasListeners
10. runtimeType
11. selectedGroup
12. Methods
13. addGroup
14. addListener
15. changeCurrentGroup
16. deselectAll
17. dispose
18. init
19. noSuchMethod
20. notifyListeners
21. onChangeCowGroupName
22. removeCowGroup
23. removeListener
24. selectGroup
25. toString
26. Operators
27. operator ==