Send a message to the peer (using the correct SMTP line terminators
        (usually only called from the SMTPSession).

def push(self, code, msg=None):
        """Send a message to the peer (using the correct SMTP line terminators
        (usually only called from the SMTPSession)."""
        if msg is None:
            msg = str(code)
        else:
            msg = '%s %s' % (code, msg)

        if not msg.endswith(self.LINE_TERMINATOR):
            msg += self.LINE_TERMINATOR
        self._channel.write(msg)