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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 run(self):
 """ Start driving the chain, block until done """

        with self._run_lock:
            while self.mounts:
                for mount in self.mounts:
                    try:
                        next(mount)
                    except StopIteration:
                        self.mounts.remove(mount)