def test_update_slice_fail(self):
        method = DataPoint.objects.all()[:2].update
        self.assertRaises(AssertionError, method,
            another_value='another thing')
Get a file from GridFS by ``"_id"``.
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.4/tests/modeltests/update/tests.py/AdvancedTests.test_update_slice_fail--crossover with--dataset/ETHPy150Open mongodb/mongo-python-driver/gridfs/__init__.py/GridFS.get