def add_node(self, addr):
        """
        When a new message queue node is in, firstly will add the address
        to the known queue nodes, then a backup for this node will be created.
        """
        if self.addrs in addr: return
        
        self.addrs.append(addr)
        
        backup_store_dir = os.path.join(self.dir_, BACKUP_STORE_FN)
        backup_node_dir = addr.replace(':', '_')
        backup_path = os.path.join(backup_store_dir, backup_node_dir)
        self.backup_stores[addr] = Store(backup_path, 
                                         size=512*1024, mkdirs=True)
dataset/ETHPy150Open chineking/cola/cola/core/mq/node.py/LocalMessageQueueNode.add_node/swapped operands of `in`