Given the following Morris inorder traversal code, what is the final output list after running inorderTraversal on this tree?

Given the following Morris inorder traversal code, what is the final output list after running inorderTraversal on this tree?

Tree structure:
2
/ \ 1 3

from typing import Optional, List

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

def inorderTraversal(root: Optional[TreeNode]) -> List[int]:
    result = []
    current = root
    while current:
        if not current.left:
            result.append(current.val)  # visit node
            current = current.right
        else:
            predecessor = current.left
            while predecessor.right and predecessor.right != current:
                predecessor = predecessor.right
            if not predecessor.right:
                predecessor.right = current  # create thread
                current = current.left
            else:
                predecessor.right = None  # remove thread
                result.append(current.val)  # visit node
                current = current.right
    return result