def old_path_from_new_path(path: str) ->str:
    """Convert a new path to an old one.

    Useful for bucket migration. This is an example implementation.
    """
    parts = path.split('/')
    filename = parts[-1]
    md5 = filename.split('.')[0]
    first_dir = parts[0]
    namespace = ''.join(filter(str.isnumeric, first_dir))
    return namespace + '-' + md5
