def undefine(self):
if lib.EnvUndefmessageHandler(self._env, self._cls, self._idx) != <NUM_LIT:1>:<EOL><INDENT>raise CLIPSError(self._env)<EOL><DEDENT>self._env = None<EOL>
Undefine the MessageHandler.

        Python equivalent of the CLIPS undefmessage-handler command.

        The object becomes unusable after this method has been called.