namespace Beam.Fluent {
public static partial class DownloadBuilder<RawType, OutType> {
        public interface IAlternativeTransformStage {
            IContextStage WithTransformer(AsyncTransformer<RawType, OutType> transformer);
            IContextStage WithTransformer(Func<RawType, OutType> transformer) {
                return WithTransformer(rt => Task.FromResult(transformer(rt)));
            }
        }
    }
}