toJson method Null safety

Implementation

Map<String, dynamic> toJson() {
  final Map<String, dynamic> data = new Map<String, dynamic>();
  data['userId'] = this.userId;
  data['roomId'] = this.roomId;
  data['x'] = this.x;
  data['y'] = this.y;
  data['width'] = this.width;
  data['height'] = this.height;
  data['zOrder'] = this.zOrder;
  data['streamType'] = this.streamType;
  data['pureAudio'] = this.pureAudio;
  return data;
}