Binding Card.IO - Class cannot have multiple base classes

I am trying to bind Card.IO with Xamarin Studio. I am getting the error "Classses cannot have multiple base classes." The line of code is here :

public sealed partial class CardIOActivity : global::Android.App.Activity, global::IO.Card.Payment.IN {

Does anyone know the line of code needed in Metadata.xml to remove one of these base classes?

Thanks