我使用python3的leetcode 257有一个错误的答案问题

Question

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

class Solution:
    def construct_paths(self,root, path='',paths =[]):
        if root:
            path += str(root.val)
            if not root.left and not root.right:
                paths.append(path)
            else:
                path += '->'
                self.construct_paths(root.left, path)
                self.construct_paths(root.right, path)
        return paths


    def binaryTreePaths(self, root):
        """
        :type root: TreeNode
        :rtype: List[str]
        """
        if not root:
            return []
        else:
            return self.construct_paths(root)

        if not root.left and not root.right:
            return [str(root.val)]

提交代码时，我收到以下错误答案： 输入： [1] 输出： [“ 1-> 2-> 5”，“ 1-> 3”，“ 1”] 预期： [“ 1”] 但是当我在测试用例中输入错误的输入时： 您的输入 [1] 输出量 [“ 1”] 预期 [“ 1”]