Python Tkinter Treeview -如何确定是否显示最后一个子级？

import tkinter as tk
from tkinter import ttk

def show_last_child(event):
    item_id = tree.focus()  # 获取当前选中的项
    child_count = tree.get_children(item_id)  # 获取子项数量
    last_child = tree.get_children(item_id)[-1]  # 获取最后一个子级的ID

    if tree.index(last_child) == len(child_count) - 1:
        # 如果最后一个子级的索引等于子项数量减一，则显示最后一个子级
        tree.item(last_child, open=True)
    else:
        # 否则，隐藏最后一个子级
        tree.item(last_child, open=False)

root = tk.Tk()

tree = ttk.Treeview(root)
tree.pack()

# 添加示例数据
item1 = tree.insert("", "end", text="Item 1")
item2 = tree.insert("", "end", text="Item 2")
item3 = tree.insert("", "end", text="Item 3")

subitem1 = tree.insert(item1, "end", text="Subitem 1")
subitem2 = tree.insert(item1, "end", text="Subitem 2")
subitem3 = tree.insert(item1, "end", text="Subitem 3")

tree.bind("<Button-1>", show_last_child)

root.mainloop()