How to change value type after type check

[zjaper456]

my code

_, ata_ret, id_data = ata.identify_device()
check.not_equal(ata_ret, None)
check.equal(ata_ret.status & 0x1, 0)

the ata_ret type is Union[ATAReturn, FixedATAReturn, None]

@staticmethod
def not_equal(value: Any, expect: Any) -> None:
    assert value != expect

i got a error info Item "None" of "Union[ATAReturn, FixedATAReturn, None]" has no attribute "status"mypy(error)

how can i fix it?

[jeremyn]

Try using the TypeGuard feature, particularly the "more than one argument" variant described in the Specification section of the linked PEP.