Convert BST to Greater Tree Python Solution

lcpy gen -n 538   # by problem number
lcpy gen -s convert_bst_to_greater_tree   # by problem name

Input: root = [4,1,6,0,2,5,7,null,null,null,3,null,null,null,8]
Output: [30,36,21,36,35,26,15,null,null,null,33,null,null,null,8]

Input: root = [0,null,1]
Output: [1,null,1]

from leetcode_py import TreeNode


class Solution:
    # Time: O(n)
    # Space: O(h) recursion stack
    def convert_bst(self, root: TreeNode[int] | None) -> TreeNode[int] | None:
        def reverse_inorder(node: TreeNode[int] | None) -> None:
            nonlocal total
            if node is None:
                return
            reverse_inorder(node.right)
            total += node.val
            node.val = total
            reverse_inorder(node.left)

        total = 0
        reverse_inorder(root)
        return root