如何让scrollview在python tkinter中强制向下滚动？

import tkinter as tk

def on_mousewheel(event):
    canvas.yview_scroll(int(-1*(event.delta/120)), "units")

root = tk.Tk()
root.geometry("400x300")

canvas = tk.Canvas(root)
canvas.pack(side=tk.LEFT, fill=tk.BOTH, expand=True)

scrollbar = tk.Scrollbar(root, command=canvas.yview)
scrollbar.pack(side=tk.RIGHT, fill=tk.Y)

canvas.configure(yscrollcommand=scrollbar.set)
canvas.bind_all("<MouseWheel>", on_mousewheel)

frame = tk.Frame(canvas)
canvas.create_window((0, 0), window=frame, anchor="nw")

# 添加内容到frame中
for i in range(50):
    label = tk.Label(frame, text=f"Label {i}")
    label.pack()

frame.update_idletasks()
canvas.configure(scrollregion=canvas.bbox("all"))

root.mainloop()