In Clean Architecture boundaries are interfaces, which I model in Python with abstract classes. The input boundary, which is between the controller and the interactor/use case does not need an interface in my opinion, since it just executes the use cases coming from a "higher level". Is this true?
Other boundaries make sense to me having interfaces, because they decouple from the implementation of my presenter/database/api etc. and because they are called from the use case. If I want to interchange the database for example I just use my interface (my abstract class) in order to implement a new database call.