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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 get_registered_configs(self, instances=None):
 """ Return the persisted values of all config files registered with the config manager. """

        configs = self.state.get('config_files', {})
        if instances is not None:
            for config_file, config in configs.items():
                if config['instance_name'] not in instances:
                    configs.pop(config_file)
        return configs