Set all attributes and unset attributes by using a value of 'null'.

def update_attributes(self, id, old_attrs, new_attrs):
        """
        Set all attributes and unset attributes by using a value of 'null'.
        """
        update = dict()
        set_value = {'attributes.' + k: v for k, v in new_attrs.items() if v is not None}
        if set_value:
            update['$set'] = set_value
        unset_value = {'attributes.' + k: v for k, v in new_attrs.items() if v is None}
        if unset_value:
            update['$unset'] = unset_value

        if update:
            response = self.get_db().alerts.update_one({'_id': {'$regex': '^' + id}}, update=update)
            return response.matched_count > 0