Tell anyone who wants to know that a sensor was updated.

def alert(self, msg):
        """Tell anyone who wants to know that a sensor was updated."""
        if self.event_callback is not None:
            try:
                self.event_callback(msg)
            except Exception as exception:  # pylint: disable=broad-except
                _LOGGER.exception(exception)

        if self.persistence:
            self.persistence.need_save = True