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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 reanimate(self, _time=None):
 """ Move dead proxies to unchecked if a backoff timeout passes """

        n_reanimated = 0
        now = _time or time.time()
        for proxy in list(self.dead):
            state = self.proxies[proxy]
            assert state.next_check is not None
            if state.next_check <= now:
                self.dead.remove(proxy)
                self.unchecked.add(proxy)
                n_reanimated += 1
        return n_reanimated