Set the urn

        :param value: URN to be saved
        :raises: *TypeError* when the value is not URN compatible

def urn(self, value: Union[URN, str]):
        """ Set the urn

        :param value: URN to be saved
        :raises: *TypeError* when the value is not URN compatible

        """
        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