code: def token(self, value):
          
          if value is None:
              self._token = value
              return
          if not isinstance(value, str):
              value = str(value)
          if len(value) > 256:
              raise AttributeError
          self._token = value
docs: Set the Token of the message.
  
          :type value: String
          :param value: the Token
          :raise AttributeError: if value is longer than 256