syntax highlight error

[daidai21]

I use leetcode now about this syntax.

This abnormal when I open the Plugin name of Python for VSCode.

This normal when I close the Plugin name of Python for VSCode.
This is code:

class Solution:
    def __init__(self):
        self.total = 0

    def convertBST(self, root: 'TreeNode') -> 'TreeNode':
        if root is not None:
            self.convertBST(root.right)
            self.total += root.val
            root.val = self.total
            self.convertBST(root.left)
        return root


# 优化
# Runtime: 80 ms, faster than 99.43% of Python3 online submissions for Convert BST to Greater Tree.
# Memory Usage: 14.9 MB, less than 2.62% of Python3 online submissions for Convert BST to Greater Tree.