给定一个二叉树，返回每一层中最大的节点值，结果以数组形式返回，现有如下代码，横线处应填入（）：

from collections import deque
import math
from typing import List, Optional

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

def largestValues(root: Optional[TreeNode]) -> List[int]:
    result = []
    if not root:
        return result

    queue = deque([root])

    while queue:
        level_size = len(queue)
        max_val = -math.inf

        for _ in range(level_size):
            _________________________

            if node.left:
                queue.append(node.left)
            if node.right:
                queue.append(node.right)

        result.append(max_val)
    return result