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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 start(self):
 """ Iterates over the `watched_configurabes` attribute and starts a config file monitor for each. The resulting observer threads are kept in an `observers` list attribute. """

        for config_class in self.watched_configurables:
            monitor = ConfigFileMonitor(config_class, self.config_dir)
            self.observers.append(
                monitor.start(
                    self.add_configurable,
                    self.update_configurable,
                    self.remove_configurable
                )
            )

        wait_on_event(self.shutdown)