GroupShareKit for GS 2017 example not working

https://github.com/sdl/groupsharekit.net lists following usage example:

var groupShareClient = await GroupShareClient.AuthenticateClient(userName,
                password,
                new Uri("http://yourgroupshareaddress"),
                GroupShareClient.AllScopes);

var users = await groupShareClient.User.GetAllUsers();

foreach (var user in users)
{
    Console.WriteLine(user.DisplayName +" loves Groupshare!");
}

However, there is neither a method "GroupShareClient.AuthenticateClient" nor a method "GetAllUsers" with the respective parameters in the GroupShareKit.
Am I missing something?