NotificationService constructor Null safety

1. diginote
2. notification_service
3. NotificationService
4. NotificationService constructor

NotificationService class

1. Constructors
2. NotificationService
3. Properties
4. hashCode
5. localNotifications
6. runtimeType
7. Methods
8. init
9. noSuchMethod
10. toString
11. Operators
12. operator ==