def past_heating_level(self, num):
        """Return a heating level from the past."""
        if num > 9:
            return 0

        try:
            if self.side == 'left':
                level = self.device.device_data_history[
                    num]['leftHeatingLevel']
            elif self.side == 'right':
                level = self.device.device_data_history[
                    num]['rightHeatingLevel']
            return level
        except TypeError:
            return 0
Return a heating level from the past.