def delete(self, doc):
        if doc.id is None:
            raise DatabaseException('Document does not have id')
        if doc.sid is None:
            try:
                rs = self.db.docs.remove({'id': doc.id}, safe=True)
                assert rs['n'] == 1
            except Exception as e:
                raise DatabaseException(e)
            return None
        doc.data = None
        return self.update(doc)
def test_contains_itself(self):
        class Recursive(Structure):
            pass

        try:
            Recursive._fields_ = [("next", Recursive)]
        except AttributeError as details:
            self.assertTrue("Structure or union cannot contain itself" in
                            str(details))
        else:
            self.fail("Structure or union cannot contain itself")