secondary property Null safety

1. Flutter
2. core_palette
3. CorePalette
4. secondary property

CorePalette class

1. Constructors
2. fromList
3. Properties
4. error
5. hashCode
6. neutral
7. neutralVariant
8. primary
9. runtimeType
10. secondary
11. tertiary
12. Methods
13. asList
14. noSuchMethod
15. toString
16. Operators
17. operator ==
18. Static methods
19. of
20. Constants
21. size