def handle_REGISTER_request(self, message, host_port):
        """
        Handle a registration request.

        Currently registration is not proxied.
        """
        (host, port) = host_port
        if self.portal is None:
            # There is no portal.  Let anyone in.
            self.register(message, host, port)
        else:
            # There is a portal.  Check for credentials.
            if "authorization" not in message.headers:
                return self.unauthorized(message, host, port)
            else:
                return self.login(message, host, port)

        Handle a registration request.

        Currently registration is not proxied.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/protocols/sip.py