toJson method Null safety

String toJson()

Implementation

String toJson() => jsonEncode(<String,String?>{
    "ownershipId" : String.fromCharCodes(ownershipId),
    "destination" : destination.toJson(),
    "about" : about,
    "reward" : reward,
    "transactionId" : String.fromCharCodes(transactionId!),
    "expiry" : expiry?.millisecondsSinceEpoch.toString()
  });