我在Python中的级别顺序遍历函数有问题

def traverse_levels_recursive(levels):
    if levels is None:
        return
    for level in levels:
        # 执行相应的操作
        print(level)
        # 递归调用遍历下一级别
        traverse_levels_recursive(level.children)

from collections import deque

def traverse_levels_queue(levels):
    if levels is None:
        return
    queue = deque()
    queue.append(levels)
    while queue:
        level = queue.popleft()
        # 执行相应的操作
        print(level)
        # 将子级别添加到队列末尾
        if level.children:
            queue.extend(level.children)