def __init__(self, *args):
        """
        @param args: Arguments for L{SMTPFactory.__init__}

        @see: L{SMTPFactory.__init__}
        """
        SMTPFactory.__init__(self, *args)
        self.challengers = {
            b'CRAM-MD5': CramMD5Credentials
        }

        @param args: Arguments for L{SMTPFactory.__init__}

        @see: L{SMTPFactory.__init__}
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/protocols.py