I have some problems when I try to get some data from the StreamTransform 

I can´t understand what is the proper data type here 

Uncaught exception:
TypeError: Instance of '\_StreamHandlerTransformer': type '\_StreamHandlerTransformer' is not a subtype of type 'StreamTransformer, dynamic>

```
import 'dart:async';
class Cake{}

class Order{
  String type;
  Order(this.type);
}

void main(){
  final controller = new StreamController();

  final order = new Order('vainilla');

 final baker = StreamTransformer.fromHandlers(
       handleData: (cakeType, sink){
           print(cakeType); 
           if(cakeType == 'chocolate'){
              sink.add(new Cake());
           }else{
             sink.addError("No puedo hacer este pastel");
           }
       } 
 );   

  controller.sink.add(order);
  controller.stream
    .map((resp) =>  { print(resp.type) } ) //maybe the sour of  the problem type is here 
    .transform(baker)
    .listen( (cake) => print('aquí esta su pastel $cake'),
              onError: (err) => print(err) 
           );
}

```