def flatten(self):
        yield self
        for expr in self.get_source_expressions():
            if expr:
                for inner_expr in expr.flatten():
                    yield inner_expr
A UNIXAddress referring to a C{None} address does not compare equal to a
dataset/ETHPy150Open django/django/django/db/models/expressions.py/BaseExpression.flatten--crossover with--dataset/ETHPy150Open nlloyd/SubliminalCollaborator/libs/twisted/internet/test/test_address.py/EmptyUNIXAddressTestCase.test_comparisonOfLinkedFiles