How to implement InAppPurchase sample in libgdx game?

Hello, Maybe I’m going to ask a silly question but is there a tutorial or reference information on the use of an InAppPurchase sample in libgdx game.

Have a look at https://github.com/multi-os-engine/moe-samples-java/tree/master/InAppPurchase
or https://github.com/libgdx/gdx-pay/tree/master/gdx-pay-iosmoe-apple/src/main/java/com/badlogic/gdx/pay/ios/apple