'Return the most recently update history for the user.
If user is anonymous, return the current history. If the user is anonymous
and the current history is deleted, return None.'

def most_recent(self, user, filters=None, current_history=None, **kwargs):

    if self.user_manager.is_anonymous(user):
        return (None if ((not current_history) or current_history.deleted) else current_history)
    desc_update_time = desc(self.model_class.table.c.update_time)
    filters = self._munge_filters(filters, (self.model_class.user_id == user.id))
    return self.query(filters=filters, order_by=desc_update_time, limit=1, **kwargs).first()
