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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_option(config, supplement, section, option, fallback=None):
 """ Reads an option for a configuration file. :param configparser.ConfigParser config: The main config file. :param configparser.ConfigParser supplement: The supplement config file. :param str section: The name of the section op the option. :param str option: The name of the option. :param str|None fallback: The fallback value of the option if it is not set in either configuration files. :rtype: str :raise KeyError: """

        if supplement:
            return_value = supplement.get(section, option, fallback=config.get(section, option, fallback=fallback))
        else:
            return_value = config.get(section, option, fallback=fallback)

        if fallback is None and return_value is None:
            raise KeyError("Option '{0!s}' is not found in section '{1!s}'.".format(option, section))

        return return_value