def undefine(self):
if lib.EnvUndefglobal(self._env, self._glb) != <NUM_LIT:1>:<EOL><INDENT>raise CLIPSError(self._env)<EOL><DEDENT>self._env = None<EOL>
Undefine the Global.

        Python equivalent of the CLIPS undefglobal command.

        The object becomes unusable after this method has been called.