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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 list_running_zones(self):
 """ Returns the currently active relay. :returns: Returns the running relay number or None if no relays are active. :rtype: string """


        self.update_controller_info()

        if self.running is None or not self.running:
            return None
        return int(self.running[0]['relay'])