def METHOD_NAME(self, assertion: bool = True, user=None):
    """Helper function to check ownership control."""
    if user is None:
        user = self.user
    item = StockItem.objects.get(pk=self.test_item_id)
    self.assertEqual(assertion, item.check_ownership(user))
    location = StockLocation.objects.get(pk=self.test_location_id)
    self.assertEqual(assertion, location.check_ownership(user))