anchor.diff:            this._selection.removeAt(i);
           }
         }     
  - 
  -      dispatchEvent(new CustomEvent('polymer-select', 
  -          detail: {'item': item, 'isSelected':  isSelected}));
  -      //this.fire('polymerselect',detail: {'item': item, 'isSelected':  isSelected});
  +
  +      this.fire('polymerselect',detail: {'item': item, 'isSelected':  isSelected});
             
       }
     }
  
positive.code:   
    PolymerSelection.created() : super.created();
    
    static const EventStreamProvider<CustomEvent> _polymerSelectEvent =
        const EventStreamProvider<CustomEvent>('polymer-select');
    
    Stream<CustomEvent> get onPolymerSelect =>
        PolymerSelection._polymerSelectEvent.forTarget(this);
  
    /**
     * Retrieves the selected item(s). If the multi property is true,
  
negative.code: 
  library polymer_elements.polymer_selection;
  
  import 'package:polymer/polymer.dart';
  
  @CustomTag('polymer-selection')
  