That meaning could be "private use". In langcodes, we check the language subtag, script, territory, and variants for validity. We don't check other parts such as extlangs or Unicode extensions. For example, ja is a valid language code, and jp is not: >>> Language.get('ja').is_...
The collaborative development of stories can enhance rapport, enable clients to gain a new perspective upon their problems, increase personal impact and clarity of meaning, and reinforce clients’ motivation to effect therapeutic change. This was found to be a particularly beneficial strategy for ...