How to import library in DartPad?

I wrote the below code in Dartpad and it return me this error:

Error compiling to JavaScript: unsupported import:

package:collection/collection.dart

import "package:collection/collection.dart";

main(List<String> args) {
  
  var data = [
    {"title": 'Avengers', "release_date": '10/01/2019'},
    {"title": 'Creed', "release_date": '10/01/2019'},
    {"title": 'Jumanji', "release_date": '30/10/2019'},
  ];
  
  var newMap = groupBy(data, (obj) => 
                       (obj as dynamic)['release_date']
                      );
  print(newMap);
  
}

Is there any way to resolve it?

After waiting... It seems that the issue has solved by the new update of dartpad.dev website.