请教老师，为什么我这么写的遍历结果不对？
class TreeNode(object):
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None
        self.traverse_path = []


class Solution(object):
    def __init__(self):
        self.traverse_path = []

    def midTraverse(self, root):
        if root:
            self.midTraverse(root.left)
            self.traverse_path.append(root.val)
            self.midTraverse(root.right)


def main():
    s = Solution()
    tree = TreeNode(3)
    tree.left = TreeNode(1)
    right = TreeNode(4)
    right.l = TreeNode(3)
    right.r = TreeNode(6)
    tree.right = right
    s.midTraverse(tree)
    print('debug path:', s.traverse_path)


if __name__ == '__main__':
    main()