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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _store_cached_zone_variable(self, zone_id, name, value):
 """ Stores the current known value of a zone variable into the cache. Calls any zone callbacks. """

        zone_state = self._zone_state.setdefault(zone_id, {})
        name = name.lower()
        zone_state[name] = value
        logger.debug("Zone Cache store %s.%s = %s",
                     zone_id.device_str(), name, value)
        for callback in self._zone_callbacks:
            callback(zone_id, name, value)