def test_callable_default(self):
        a = Foo.objects.create(id=1, a='abc', d=Decimal('12.34'))
        b = Bar.objects.create(b='bcd')
        self.assertEqual(b.a, a)
A lazy callable may be used for ForeignKey.default.
dataset/ETHPy150Open django/django/tests/model_fields/test_foreignkey.py/ForeignKeyTests.test_callable_default