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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_contour_yaml(config_file=__file__, names=None):
 """ Traverse directory trees to find a contour.yaml file Begins with the location of this file then checks the working directory if not found Args: config_file: location of this file, override for testing Returns: the path of contour.yaml or None if not found """

    checked = set()
    contour_yaml = _find_countour_yaml(os.path.dirname(config_file), checked,
                                       names=names)

    if not contour_yaml:
        contour_yaml = _find_countour_yaml(os.getcwd(), checked, names=names)

    return contour_yaml