APIObject constructor Null safety

1. conduit_open_api
2. open_api_v3
3. APIObject
4. APIObject constructor

APIObject class

1. Constructors
2. APIObject
3. Properties
4. castMap
5. extensions
6. hashCode
7. referenceURI
8. runtimeType
9. Methods
10. decode
11. encode
12. noSuchMethod
13. toString
14. Operators
15. operator ==