def default_classdata(_, index):
    """Load default classdata if no class data is passed
    Args:
        _: Ignored path value
        index: Index file dictionary
    Returns:
        classes: A list of image classes
        class_to_idx: Mapping from classes to indexes of those classes
    """
    classes = list(index.keys())
    classes.sort()
    class_to_idx = {classes[i]: i for i in range(len(classes))}
    return classes, class_to_idx