Cleanup all the expired keys

def cleanup(self):
        """Cleanup all the expired keys"""
        keys = self.client.smembers(self.keys_container)
        for key in keys:
            entry = self.client.get(key)
            if entry:
                entry = pickle.loads(entry)
                if self._is_expired(entry, self.timeout):
                    self.delete_entry(key)