def getChallenge(self, address):
        """
        Generate the challenge for use in the WWW-Authenticate header.

        @param address: The client address to which this challenge is being
            sent.

        @return: The L{dict} that can be used to generate a WWW-Authenticate
            header.
        """
        c = self._generateNonce()
        o = self._generateOpaque(c, address)

        return {'nonce': c,
                'opaque': o,
                'qop': b'auth',
                'algorithm': self.algorithm,
                'realm': self.authenticationRealm}

        Generate the challenge for use in the WWW-Authenticate header.

        @param address: The client address to which this challenge is being
            sent.

        @return: The L{dict} that can be used to generate a WWW-Authenticate
            header.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/cred/credentials.py