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class Solution:
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    def trimBST(self, root: TreeNode, low: int, high: int) -> TreeNode:
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        if not root:
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            return root
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        if root.val < low:
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            return self.trimBST(root.right, low, high)
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        if root.val > high:
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            return self.trimBST(root.left, low, high)
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        root.left = self.trimBST(root.left, low, high)
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        root.right = self.trimBST(root.right, low, high)
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        return root