# Definition for a binary tree node.# class TreeNode:#     def __init__(self, x):#         self.val = x#         self.left = None#         self.right = Noneclass Solution:    def isSameTree(self, p: TreeNode, q: TreeNode) -> bool:        # 如果两棵树都不存在，返回True        if p is None and q is None:            return True                # 如果两棵树都存在        if p is not None and q is not None:            return p.val == q.val and self.isSameTree(p.left, q.left) and self.isSameTree(p.right, q.right)                # 一棵树存在一棵树不存在        return False