code: def urn(self, value: Union[URN, str]):
          
          if isinstance(value, str):
              value = URN(value)
          elif not isinstance(value, URN):
              raise TypeError("New urn must be string or {} instead of {}".format(type(URN), type(value)))
          self._urn = value
docs: Set the urn
  
          :param value: URN to be saved
          :raises: *TypeError* when the value is not URN compatible