def test_invalid_assignment_downwards(self):
        C = self.classes.C

        sess = Session()
        c1 = C()
        c1.class_name = 'b'
        sess.add(c1)
        assert_raises_message(
            sa_exc.SAWarning,
            "Flushing object %s with incompatible "
            "polymorphic identity 'b'; the object may not "
            "refresh and/or load correctly" % instance_str(c1),
            sess.flush
        )
test that we warn on assign of 'b' to a C, since this adds
dataset/ETHPy150Open zzzeek/sqlalchemy/test/orm/inheritance/test_basic.py/PolymorphicAttributeManagementTest.test_invalid_assignment_downwards