def METHOD_NAME(self, green_asn, checker):
    """
    Sometimes the service we use for resolving ASNs returns
    an empty result.
    """
    green_asn.save()
    checker.asn_from_ip = mock.MagicMock(return_value=None)
    res = checker.check_domain("100.113.75.254")
    assert isinstance(res, legacy_workers.SiteCheck)