N 叉树的层序遍历

def solve(____):
    from collections import deque
    if not root:
        return []
    result, q = [], deque(____)
    while q:
        level = []
        for _ in range(len(____)):
            node = q.popleft()
            level.append(____)
            for child in node.children:
                q.append(____)
        result.append(____)
    return result