MapBase class

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