def format_path_data(path_data):
    """
    Args:
        path_data (list or str): Either a list of paths, or just one path.

    Returns:
        list: A list of paths
    """
    assert isinstance(path_data, str) or isinstance(path_data, list)
    if isinstance(path_data, str):
        path_data = [path_data]
    return path_data