ThetaBase constructor Null safety

1. theta
2. theta
3. ThetaBase
4. ThetaBase constructor

ThetaBase class

1. Constructors
2. ThetaBase
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. noSuchMethod
8. toString
9. Operators
10. operator ==
11. Static properties
12. baseUrl
13. contentType
14. dio
15. Static methods
16. get
17. post
18. Constants
19. emptyMap