code: def _convert_default_value(self, default):
          if default is None:
              return None
          if isinstance(default, str):
              if self.special_type == 'string':
                  return default.encode('utf-8') + b'\0'
              raise DataError("You can only pass a unicode string if you are declaring a string type config variable", default=default)
          if isinstance(default, (bytes, bytearray)):
              if self.special_type == 'string' and isinstance(default, bytes):
                  default += b'\0'
              return default
          if isinstance(default, int):
              default = [default]
          format_string = "<" + (self.base_type*len(default))
          return struct.pack(format_string, *default)