Maximum Depth of N-ary Tree Python Solution

lcpy gen -n 559   # by problem number
lcpy gen -s maximum_depth_of_n_ary_tree   # by problem name

Input: root = [1,null,3,2,4,null,5,6]
Output: 3

Input: root = [1,null,2,3,4,5,null,null,6,7,null,8,null,9,10,null,null,11,null,12,null,13,null,null,14]
Output: 5

from __future__ import annotations


class NaryNode:
    def __init__(self, val: int = 0, children: list[NaryNode] | None = None) -> None:
        self.val = val
        self.children = children if children is not None else []


class Solution:
    # Time: O(n)
    # Space: O(w)
    def max_depth(self, root: NaryNode | None) -> int:
        if root is None:
            return 0
        depth = 0
        level: list[NaryNode] = [root]
        while level:
            depth += 1
            next_level: list[NaryNode] = []
            for node in level:
                next_level.extend(node.children)
            level = next_level
        return depth