遍历树NLP python。如何使用DFS方法查找VP子树以找到子树中最深的动词

class TreeNode:
    def __init__(self, value):
        self.value = value
        self.children = []

def dfs(node):
    if node is None:
        return None
    
    # 如果当前节点是动词节点，返回该节点
    if node.value == "动词":
        return node
    
    # 遍历子节点
    for child in node.children:
        result = dfs(child)
        if result is not None:
            return result
    
    return None

def find_deepest_verb(root):
    deepest_verb = None
    max_depth = -1
    
    def dfs(node, depth):
        nonlocal deepest_verb, max_depth
        
        if node is None:
            return
        
        if node.value == "动词" and depth > max_depth:
            deepest_verb = node
            max_depth = depth
        
        for child in node.children:
            dfs(child, depth + 1)
    
    dfs(root, 0)
    
    return deepest_verb

# 构建树
root = TreeNode("S")
vp = TreeNode("VP")
v1 = TreeNode("动词")
v2 = TreeNode("动词")
vp.children = [v1, v2]
root.children = [vp]

# 查找最深的动词节点
deepest_verb = find_deepest_verb(root)

# 输出结果
if deepest_verb is not None:
    print("最深的动词节点是:", deepest_verb.value)
else:
    print("未找到动词节点")