def setDag(self, dag):
        self.clear()
        self.dag = dag
Test that annotating None onto a model round-trips
dataset/ETHPy150Open andrew-gardner/dependsworkflow/depends/depends_graphics_widgets.py/SceneWidget.setDag--crossover with--dataset/ETHPy150Open django/django/tests/annotations/tests.py/NonAggregateAnnotationTestCase.test_null_annotation