What does it mean when a public function in RecyclerView.Adapter exposes its internal return type in Kotlin?

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When a public function in RecyclerView.Adapter exposes its internal return type in Kotlin, it means that the function is making its internal implementation details available to external code. This can be useful in some cases, such as when a developer wants to access or modify the data held by the adapter. However, it can also lead to potential problems, such as breaking encapsulation and making the adapter more difficult to maintain. Care should be taken when exposing internal implementation details in public functions to ensure that it is done appropriately and with consideration for the overall design of the code.