Convert BST to Greater Tree.md

Given a Binary Search Tree (BST), convert it to a Greater Tree such that every key of the original BST is changed to the original key plus sum of all keys greater than the original key in BST.

Example:

Input: The root of a Binary Search Tree like this:
              5
            /   \
           2     13

Output: The root of a Greater Tree like this:
             18
            /   \
          20     13

My code:

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def convertBST(self, root):
        """
        :type root: TreeNode
        :rtype: TreeNode
        """
        if root==None:
            return None
        self.convertBST1(root,0)
        return root
    def convertBST1(self,root,tmp_sum):
        if root==None:
            return 0
        right_sum=0
        if root.right!=None:
            right_sum=self.convertBST1(root.right,tmp_sum)
        
            root.val+=right_sum
        else:
            root.val+=tmp_sum
        left_sum=root.val
        if root.left!=None:
            left_sum=self.convertBST1(root.left,root.val)
        return left_sum

Solution: https://leetcode.com/problems/convert-bst-to-greater-tree/