UnmodifiableMapMixin<K, V> constructor Null safety

1. Flutter
2. collection
3. UnmodifiableMapMixin<K, V>
4. UnmodifiableMapMixin constructor

UnmodifiableMapMixin class

1. Constructors
2. UnmodifiableMapMixin
3. Properties
4. entries
5. first
6. hashCode
7. isEmpty
8. isNotEmpty
9. keys
10. last
11. length
12. runtimeType
13. values
14. Methods
15. addAll
16. addEntries
17. cast
18. clear
19. containsKey
20. containsValue
21. forEach
22. map
23. noSuchMethod
24. putIfAbsent
25. remove
26. removeWhere
27. toString
28. update
29. updateAll
30. Operators
31. operator ==
32. operator []
33. operator []=