The service's eventable variables.

        Returns:
            list(tuple): A list of (variable name, data type) tuples.

def event_vars(self):
        """The service's eventable variables.

        Returns:
            list(tuple): A list of (variable name, data type) tuples.
        """
        if self._event_vars is None:
            self._event_vars = list(self.iter_event_vars())
        return self._event_vars