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