Longest Univalue Path LeetCode solution in Python

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class Solution:
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    max_path = 0
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    def longestUnivaluePath(self, root: Optional[TreeNode]) -> int:
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        self.dfs(root)
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        return self.max_path
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    def dfs(self, root):
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        if root is None:
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            return 0
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        left = self.dfs(root.left)
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        right = self.dfs(root.right)
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        if root.left and root.left.val == root.val:
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            leftPath = left + 1
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        else:
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            leftPath = 0
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        if root.right and root.right.val == root.val:
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            rightPath = right + 1
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        else:
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            rightPath = 0
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        self.max_path = max(self.max_path, leftPath + rightPath)
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        return max(leftPath, rightPath)