some scripting help

i am using unity 5.5 beta and i just got a plugin for google play services from here: GitHub - playgameservices/play-games-plugin-for-unity: Google Play Games plugin for Unity

and got an error saying

Assets/GooglePlayGames/ISocialPlatform/PlayGamesLocalUser.cs(27,18): error CS0535: GooglePlayGames.PlayGamesLocalUser’ does not implement interface member UnityEngine.SocialPlatforms.ILocalUser.Authenticate(System.Action)’

here is the suggested answer by Kidel but i don’t know how to implement it ! link text PlayGamesLocalUser' does not implement interface member `UnityEngine.SocialPlatforms.ILocalUser.Authenticate(System.Action<bool,string>)' · Issue #1432 · playgameservices/play-games-plugin-for-unity · GitHub

please help.

PlayGamesLocalUser script is attached with this question

What you need to do is open PlayGamesLocalUser.cs and add the method

public void Authenticate(System.Action action){

}

An interface forces a script implementing it to have all it’s members defined and that one seems to be missing