In java I can declare an interface: ``` interface ...

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[jlleitschuh]

In java I can declare an interface:

interface AnimalHolder {
    Set<? extends Animal> getAnimals();
}

And in a impl I can do do:

class CatHolder implements AnimalHolder {
   @Override
    Set<Cat> getAnimals();
}

Where Cat implements Animal
But If I convert AnimalHolder to kotlin:

interface AnimalHolder {
    val animals : Set<out Animal>
}

I can no longer have CatHandler have its getAnimals method return Set<Cat>.
What do I need to do on my interface to allow for the same behavior I can get in java?