def __init__(self, fix=False, lookup_dns=None):
        self.fix = fix
        
        if lookup_dns:
            try:
                import DNS
            except ImportError: # pragma: no cover
                raise ImportError("To enable DNS lookup of domains install the PyDNS package.")
            
            lookup_dns = lookup_dns.lower()
            if ('a', 'mx') not in lookup_dns:
                raise RuntimeError("Not a valid *lookup_dns* value: " + lookup_dns)
        
        self._lookup_dns = lookup_dns
dataset/ETHPy150Open marrow/mailer/marrow/mailer/validator.py/DomainValidator.__init__/swapped operands of `not in`