EventContext_OriginId constructor Null safety

1. spine_client
2. event.pb
3. EventContext_OriginId
4. EventContext_OriginId const constructor

EventContext_OriginId enum

1. Constructors
2. EventContext_OriginId
3. Values
4. commandId
5. eventId
6. notSet
7. Properties
8. hashCode
9. index
10. runtimeType
11. Methods
12. noSuchMethod
13. toString
14. Operators
15. operator ==
16. Constants
17. values