Json serialization for code generation not working?

Question

I have cloned a project from github and it shows error in some file and i found it was for json serilizable

part 'upload_response.g.dart';//error here

@AccountIdConverter()
@MediaTypeConverter()
@IdConverter()
@JsonSerializable()
class UploadResponse with EquatableMixin  {

  final AccountId accountId;
  final Id blobId;
  final MediaType type;
  final int size;

  UploadResponse(this.accountId, this.blobId, this.type, this.size);

  factory UploadResponse.fromJson(Map<String, dynamic> json) => _$UploadResponseFromJson(json); //error here

  Map<String, dynamic> toJson() => _$UploadResponseToJson(this);//error here

  @override
  List<Object?> get props => [accountId, blobId, type, size];
}

extension UploadResponseExtension on UploadResponse {
  Attachment toAttachmentFile(String nameFile, {MediaType? mediaType}) {
    return Attachment(blobId: blobId, size: UnsignedInt(size), name: nameFile, type: mediaType ?? type);
  }
}

i have run the command flutter pub run build_runner build and terminal shows files are generated,

but the error for the files are still

what can be the reason .