<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def cleanup(self):
 """ Release resources used by supporting classes """

        try:
            self.unload_lime()
        except AttributeError as ex:
            pass
        self.tunnel.cleanup()
        self.shell.cleanup()