fire abstract method Null safety

1. baguette
2. IEventManager
3. IEventManager
4. fire abstract method

IEventManager class

1. Constructors
2. IEventManager
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. addPlugin
8. cleanPlugins
9. fire
10. getPlugin
11. noSuchMethod
12. removePlugin
13. subscribe
14. toString
15. unsubscribe
16. Operators
17. operator ==