QueryDirection constructor Null safety

1. nim_core
2. nim_core
3. QueryDirection
4. QueryDirection const constructor

QueryDirection enum

1. Constructors
2. QueryDirection
3. Values
4. QUERY_OLD
5. QUERY_NEW
6. Properties
7. hashCode
8. index
9. runtimeType
10. Methods
11. noSuchMethod
12. toString
13. Operators
14. operator ==
15. Constants
16. values