def get_pk_values(cls, instance_or_pk):
        """Return a primary key as a tuple.

        :param instance_or_pk: An instance of this model class, or a
          primary key. A composite primary key can be passed as a
          tuple.

        """

        if isinstance(instance_or_pk, cls):
            cls._flask_signalbus_sa.session.flush()
            instance_or_pk = inspect(cls).primary_key_from_instance(instance_or_pk)
        return instance_or_pk if isinstance(instance_or_pk, tuple) else (instance_or_pk,)
Return a primary key as a tuple.

        :param instance_or_pk: An instance of this model class, or a
          primary key. A composite primary key can be passed as a
          tuple.