House Robber III LeetCode solution in Python

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class Solution:
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    def rob(self, root: Optional[TreeNode]) -> int:
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        hashMap = {}
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        def helper(root: Optional[TreeNode]) -> int:
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            if not root:
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                return 0
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            if root in hashMap:
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                return hashMap[root]
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            ansOption1 = root.val
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            if root.left is not None:
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                ansOption1 += helper(root.left.left) + helper(root.left.right)
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            if root.right is not None:
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                ansOption1 += helper(root.right.left) + helper(root.right.right)
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            ansOption2 = helper(root.left) + helper(root.right)
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            ansFinal = max(ansOption1, ansOption2)
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            hashMap[root] = ansFinal
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            return ansFinal
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        return helper(root)