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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 find_config(fname='.rdo.conf', start=None):
 """Go up until you find an rdo config. """

    start = start or os.getcwd()
    config_file = os.path.join(start, fname)
    if os.path.isfile(config_file):
        return config_file

    parent, _ = os.path.split(start)
    if parent == start:
        raise Exception('Config file not found')

    return find_config(fname, parent)