It can't show file, edit, view, color_menu

import tkinter as tk
from tkinter import ttk
from tkinter import font, colorchooser, messagebox
import os

main_application=tk.Tk()
main_application.geometry('1200x800')
main_application.title('vpad text editer')

main_menu=tk.Menu()
file = tk.Menu(main_menu, tearoff=False)
edit = tk.Menu(main_menu, tearoff=False)
view=tk.Menu(main_menu, tearoff=False)
color_theme=tk.Menu(main_menu, tearoff=False)

main_menu.add_cascade(label='file', menu=file)
main_menu.add_cascade(label='edit', menu=edit)
main_menu.add_cascade(label='view', menu=view)
main_menu.add_cascade(label='color Theme', menu=color_theme)

main_application.mainloop()