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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 release(self):
 """ Release the lock if acquired. """

        # TODO: thread safety (currently the lock may be acquired for one more TTL length)
        if self.token is not None:
            try:
                self.client.test_and_set(self.key, 0, self.token)
            except (ValueError, etcd.EtcdKeyError, etcd.EtcdKeyNotFound) as e:
                pass  # the key already expired or got acquired by someone else
            finally:
                self.token = None