Xamarin Photo Project Extension help on how to implement GetSupportedProjectTypes

In order to help community I have created a Photo Project Extension application due to Xamarin currently not providing functionality.

github.com/equinox2k/XamarinMacPhotoProjectExtension/tree/master

How ever I am stuck on how to return GetSupportedProjectTypes any help appreciated

    // This is not being called for some reason... what is this... PHProjectExtensionController_Extensions.GetSupportedProjectTypes(this);
    public PHProjectTypeDescription[] GetSupportedProjectTypes()
    {
        PHProjectTypeDescription desc = new PHProjectTypeDescription((NSString)"PHProjectTypeUndefined", "my title", "my desc", null);

        var types = new PHProjectTypeDescription[] { desc };
        // Fill the array with PHProjectTypeDescription instances representing you project types.
        // If you don't want to support custom project types set PHProjectExtensionDefinesProjectTypes to NO in the extension's Info.plist NSExtensionAttributes dictionary.
        return types;
    }