def sendCode(self, code, message=b''):
        """
        Send an SMTP code with a message.
        """
        lines = message.splitlines()
        lastline = lines[-1:]
        for line in lines[:-1]:
            self.sendLine(networkString('%3.3d-' % (code,)) + line)
        self.sendLine(networkString('%3.3d ' % (code,)) +
                                    (lastline and lastline[0] or b''))

        Send an SMTP code with a message.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/smtp.py