Unexpected Unity error

After import Amazon packages you can face with errors look like:

Source/UnitySocialAPI/AGSSocialLocalUser.cs(19,14): error CS0535: `AGSSocialLocalUser' does not implement interface member `UnityEngine.SocialPlatforms.ILocalUser.Authenticate(System.Action<bool,string>)'

or 

Source/UnitySocialAPI/GameCircleSocial.cs(20,14): error CS0535: `GameCircleSocial' does not implement interface member `UnityEngine.SocialPlatforms.ISocialPlatform.Authenticate(UnityEngine.SocialPlatforms.ILocalUser, System.Action<bool,string>)'

These errors relate with Amazon API. In order to fix it you should create two methods:

in the class AGSSocialLocalUser.cs:

public void Authenticate(System.Action<bool ,string> callback) {}

and another one in the class GameCircleSocial.cs:

public void Authenticate(ILocalUser user, System.Action<bool, string> callback) {}

That's all.