Maximum Level Sum of a Binary Tree LeetCode solution in Python

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class Solution:
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    def maxLevelSum(self, root: Optional[TreeNode]) -> int:
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        global_max = float("-inf")
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        res = -1
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        q = deque([root])
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        lvl = 1
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        while q:
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            total = 0
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            for _ in range(len(q)):
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                node = q.popleft()
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                if node.left:
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                    q.append(node.left)
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                if node.right:
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                    q.append(node.right)
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                total += node.val
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            if total > global_max:
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                res = lvl
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                global_max = total
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            lvl += 1
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        return res