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kotlinlang

I have another problem. I want to create a `Book` that has a reference to an `Author` and the `Author` has many references to many books. I want them booth to me immutable data classes. I can not create one with an empty field to then use it to create the other. How do one do that? I want to essentially create an `Author` and while creating it I want to create `Book`s that reference that `Author` I am currently creating. How do I do that?