In case of account update; there are two steps. 1. Validate; if there are any field errors, raise exception else, 2. Save The `update_user_preferences` in `preferences/api.py` does both steps for preferences.  If we call it directly then shall there exist any error in preference field `account_privacy`; it will be raised after update of other account information. That is why I explicitly validated and saved account_privacy in two steps. 