class ParamErrorException implements Exception {
  final String message;

  ParamErrorException([this.message = '参数错误']);

  @override
  String toString() => 'ParamErrorException: $message';
}

class ChunkUploadFailedException implements Exception {
  final String message;

  ChunkUploadFailedException([this.message = 'Chunk upload failed']);

  @override
  String toString() => 'ChunkUploadFailedException: $message';
}