A3L Authentication is an abstraction library for Authentication, enabling the developers to let the user sign in with their Google accounts. It supports both Android and Fire OS devices. The A3L Authentication has dependency on Google Sign In for devices with Google Play Services and AppAuth for Android devices without Google Play Services. AppAuth is a client-side SDK for native apps to authenticate and authorise end-users using OAuth 2.0 and OpenID Connect. The API structure is kept close to that of Google Sign In so that the amount of effort needed by developers to learn and implement the SDK is minimal. 

The sample apps are integrated with A3L Authentication SDK.  To run these apps, you don't need to write any code, but you must provide the configurations. You can install the apps on both Google Play-enabled devices and Fire OS devices. From the apps, you can authentication with Google and fetch the profile details and ID tokens as needed. 

A3LAuthentication-1.1.0.aar is the SDK that need to be added as dependency in your project for more detail check this https://developer.amazon.com/docs/a3l-authentication/get-started.html