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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 load_config(config_file='~/.stancache.ini'):
 """ Load config file into default settings """

    if not os.path.exists(config_file):
        logging.warning('Config file does not exist: {}. Using default settings.'.format(config_file))
        return
    ## get user-level config in *.ini format
    config = configparser.ConfigParser()
    config.read(config_file)
    if not config.has_section('main'):
        raise ValueError('Config file {} has no section "main"'.format(config_file))
    for (key, val) in config.items('main'):
        _set_value(key.upper(), val)
    return