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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def reset(self):
 """ Instruct the target to forget any related exception. """

        if not self.chain_id:
            return

        saved, self.chain_id = self.chain_id, None
        try:
            self.call_no_reply(mitogen.core.Dispatcher.forget_chain, saved)
        finally:
            self.chain_id = saved