@reflector
class FancyContainer extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(
      width: 100,
      height: 100,
      color: Colors.indigo,
    );
  }
}

@reflector
@Defaults(
  [],
  positioned: {
    'imageProvider': NetworkImage(
        "https://images.unsplash.com/photo-1546072533-675fd58d08e8?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=1000&q=80"),
    'text': "This is a nice video",
    "width": 300.0,
    "height": 150.0,
    "elevation": 8.0,
    'fit': BoxFit.cover,
  }

)
class VideoCard extends StatelessWidget {

...

}