Maximum Difference Between Node and Ancestor LeetCode solution in Python

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class Solution:
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    def maxAncestorDiff(self, root: Optional[TreeNode]) -> int:
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        self.max_diff = float("-inf")
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        def dfs(node, prev_min, prev_max):
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            if not node:
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                return
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            dfs(node.left, min(prev_min, node.val), max(prev_max, node.val))
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            dfs(node.right, min(prev_min, node.val), max(prev_max, node.val))
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            self.max_diff = max(
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                abs(node.val - prev_min), abs(node.val - prev_max), self.max_diff
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            )
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        dfs(root, root.val, root.val)
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        return self.max_diff