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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 stop(self, key):
 """ Stop a concurrent operation. This gets the concurrency limiter for the given key (creating it if necessary) and stops a concurrent operation on it. If the concurrency limiter is empty, it is deleted. """

        self._get_limiter(key).stop()
        self._cleanup_limiter(key)