def clear(self):
        self.extensions.clear()
        for ext in self.extension_kinds.values():
            self._get_store(ext).clear()
Try to update a model instance introducing a FK constraint violation.
dataset/ETHPy150Open ARM-software/workload-automation/wlauto/core/extension_loader.py/ExtensionLoader.clear--crossover with--dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.2/tests/regressiontests/backends/tests.py/FkConstraintsTests.test_integrity_checks_on_update