def do_execute(self):
        """
        The actual execution of the actor.

        :return: None if successful, otherwise error message
        :rtype: str
        """
        relname = self.resolve_option("name")
        if isinstance(self.input.payload, Instance):
            self.input.payload.dataset.relationname = relname
        else:
            self.input.payload.relationname = relname
        self._output.append(self.input)
        return None
The actual execution of the actor.

        :return: None if successful, otherwise error message
        :rtype: str