DropDowns constructor Null safety

1. equizz
2. drop_downs
3. DropDowns
4. DropDowns constructor

DropDowns class

1. Constructors
2. DropDowns
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. noSuchMethod
8. toString
9. Operators
10. operator ==
11. Static properties
12. index1
13. index2
14. index3
15. Static methods
16. dropDown