def get(self, key):
        """Retrieves the value for a key or None.

        This expunges expired keys during each get.
        """

        now = timeutils.utcnow_ts()
        for k in self.cache.keys():
            (timeout, _value) = self.cache[k]
            if timeout and timeout >= now:
                del self.cache[k]

        return self.cache.get(key, (0, None))[1]
dataset/ETHPy150Open openstack/rack/rack/openstack/common/memorycache.py/Client.get/swapped operands of `>=`