sad constant Null safety

1. wings_data_model
2. wings_data_model
3. MoodType
4. sad constant

MoodType class

1. Properties
2. hashCode
3. name
4. runtimeType
5. Methods
6. noSuchMethod
7. toString
8. Operators
9. operator ==
10. Static properties
11. serializer
12. values
13. Static methods
14. fromDatabaseFormat
15. toDatabaseFormat
16. valueOf
17. Constants
18. constantName
19. fine
20. ok
21. sad
22. unknown