Here are the implementation details:
Pass in null since this is not used.
To validate Android monetization, please enter your Google Public API Key in your Analytics dashboard Project Settings Form.
The Google Public API Key is needed for implementing receipt verification for in-app purchases (IAP) on Google Play. Your Google Public Key is under Google Play Developer console > All applications > Services & APIs > Your License Key For This Application. This is optional, but if you are developing for Android and have in-app purchases, we highly recommend implementing it.