def normalize_ident(ident):
    if isinstance(ident, tuple) and len(ident) == 2:
        return ident[0], ident[1]  # content_id, subtopic_id
    else:
        return ident, None
Splits a generic identifier.
dataset/ETHPy150Open dossier/dossier.web/dossier/web/label_folders.py/normalize_ident