convert method
Implementation
ProgressUpdate convert() {
final int bytesSent = (this.bytesSent).toInt();
final int imageSize = (this.imageSize).toInt();
final int milliseconds = (this.timestamp * 1000).toInt();
final date = DateTime.fromMillisecondsSinceEpoch(milliseconds);
return ProgressUpdate(bytesSent, imageSize, date);
}