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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 stop_services(self, *service_names):
 """ Stop one or more registered services, by name. If no service names are given, stops all registered services. """

        for service_name in service_names or self.services.keys():
            self.fire_event('stop', service_name, default=[
                manage_ports,
                service_stop])