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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 _read_configuration(config_filename):
 """ Checks the supplement file. :param str config_filename: The name of the configuration file. :rtype: (configparser.ConfigParser,configparser.ConfigParser) """

        config = ConfigParser()
        config.read(config_filename)

        if 'supplement' in config['database']:
            path = os.path.dirname(config_filename) + '/' + config.get('database', 'supplement')
            config_supplement = ConfigParser()
            config_supplement.read(path)
        else:
            config_supplement = None

        return config, config_supplement