def response_hook(self, r, **kwargs):
        """The actual hook handler."""
        if r.status_code == 401:
            # Handle server auth.
            www_authenticate = r.headers.get('www-authenticate', '').lower()
            auth_type = _auth_type_from_header(www_authenticate)

            if auth_type is not None:
                return self.retry_using_http_NTLM_auth(
                    'www-authenticate',
                    'Authorization',
                    r,
                    auth_type,
                    kwargs
                )
        elif r.status_code == 407:
            # If we didn't have server auth, do proxy auth.
            proxy_authenticate = r.headers.get(
                'proxy-authenticate', ''
            ).lower()
            auth_type = _auth_type_from_header(proxy_authenticate)
            if auth_type is not None:
                return self.retry_using_http_NTLM_auth(
                    'proxy-authenticate',
                    'Proxy-authorization',
                    r,
                    auth_type,
                    kwargs
                )

        return r
The actual hook handler.