Как объединить выпадающее меню с меню верхнего уровня в tkinter

Я пытаюсь сделать простой текстовый редактор с строкой меню и создал раскрывающееся меню, но в конце меню я хочу просто «О программе» без раскрывающегося списка, и я не могу этого сделать. Каждый раз, когда я хочу добавить его, программа работает, но не отображается на экране, как мне это сделать?

Вот мой код:

from tkinter import *
from tkinter import Menu, scrolledtext
from tkinter import messagebox

class GUI(Frame):
    def __init__(self):
        super().__init__()
        self.pack()
        self.drop_down_menu()
        #self.toolbar()
        self.text_area()


###GUI Drop-down menu
    def drop_down_menu(self):
        self.menu = Menu(root)
        root.config(menu= self.menu)

        self.submenu = Menu(self.menu)
        self.menu.add_cascade(label = "File", menu = self.submenu)
        self.submenu.add_command(label = "New", command = "")
        self.submenu.add_command(label = "Open", command = "" )
        self.submenu.add_command(label = "Open Recent", command = "")
        self.submenu.add_separator()
        self.submenu.add_command(label = "Save", command = "")
        self.submenu.add_command(label = "Duplicate", command = "" )
        self.submenu.add_command(label = "Rename", command = "")
        self.submenu.add_command(label = "Move to", command = "")
        self.submenu.add_separator()
        self.submenu.add_command(label = "Exit", command = self.exit_function)

        self.editmenu = Menu(self.menu)
        self.menu.add_cascade(label = "Edit", menu = self.editmenu)
        self.editmenu.add_command(label = "Undo", command = "")
        self.editmenu.add_command(label = "Redo", command = "" )
        self.editmenu.add_separator()
        self.editmenu.add_command(label = "Cut", command = "")
        self.editmenu.add_command(label = "Copy", command = "")
        self.editmenu.add_command(label = "Paste", command = "")
        self.editmenu.add_command(label = "Delete", command = "")
        self.editmenu.add_separator()
        self.editmenu.add_command(label = "Find", command = "")

        self.viewmenu = Menu(self.menu)
        self.menu.add_cascade(label = "View", menu = self.viewmenu)
        self.viewmenu.add_command(label = "Zoom in", command = "")
        self.viewmenu.add_command(label = "Zoom out", command = "" )
        self.viewmenu.add_separator()
        self.viewmenu.add_command(label = "Full Screen", command = "")

        self.aboutmenu = Menu(self.menu)
        self.aboutmenu.add_command(label = "About", command = "")




    # def toolbar(self):
    #     self.toolbar = Frame(root, bg = "#DCDCDC")
    #     self.toolbar.pack(side = TOP, fill = X)
    #
    #
    #     self.paragraph_button = Button(self.toolbar, text = "Paragraph style", command = "")
    #     self.paragraph_button.grid(row = 1, column = 0, columnspan= 3)
    #     self.font_button = Button(self.toolbar, text = "Font-family", command = "", height=1, width=3)
    #     self.font_button.grid(row=1, column=4)
    #     self.typeface_button = Button(self.toolbar, text = "Typeface", command = "", height=1, width=3)
    #     self.typeface_button.grid(row=1, column=5)
    #     self.font_size_button = Button(self.toolbar, text = "Font size", command = "", height=1, width=3)
    #     self.font_size_button.grid(row=1, column=6)
    #     self.font_color_button = Button(self.toolbar, text = "Font color", command = "", height=1, width=3)
    #     self.font_color_button.grid(row=1, column=7)
    #     self.bg_color_button = Button(self.toolbar, text = "Background color", command = "", height=1, width=3)
    #     self.bg_color_button.grid(row=1, column=8)
    #     self.bold_text_button = Button(self.toolbar, text = "Bold text", command = "", height=1, width=3)
    #     self.bold_text_button.grid(row=1, column=9)
    #     self.italicise_text_button = Button(self.toolbar, text = "Italicise text", command = "", height=1, width=3)
    #     self.italicise_text_button.grid(row=1, column=10)
    #     self.underline_text_button = Button(self.toolbar, text = "Underline text", command = "", height=1, width=3)
    #     self.underline_text_button.grid(row=1, column=11)
    #
    #     self.left_align_button = Button(self.toolbar, text = "Align to left", command = "", height=1, width=3)
    #     self.left_align_button.grid(row=1, column=12)
    #     self.centere_text_button = Button(self.toolbar, text = "Centere text", command = "", height=1, width=3)
    #     self.centere_text_button.grid(row=1, column=13)
    #     self.right_align_button = Button(self.toolbar, text = "Align to right", command = "", height=1, width=3)
    #     self.centere_text_button.grid(row=1, column=14)
    #     self.justify_text_button = Button(self.toolbar, text = "Justify text", command = "", height=1, width=3)
    #     self.justify_text_button.grid(row=1, column=15)
    #
    #     self.paragraph_spacing_button = Button(self.toolbar, text = "Paragraph spacing", command = "", height=1, width=3)
    #     self.paragraph_spacing_button.grid(row=1, column=16)
    #     self.paragraph_spacing_button = Button(self.toolbar, text = "Paragraph spacing", command = "", height=1, width=3)
    #     self.paragraph_spacing_button.grid(row=1, column=17)


    def text_area(self):
        textarea = scrolledtext.ScrolledText(root, width=100, height=50)
        textarea.pack()


    def exit_function(self):
        if messagebox.askyesno("Close the window", "Do you want to close the window?", icon='warning'):
            root.destroy()
        else:
            pass
    def about(self):
        messagebox.showinfo("About Greg's text editor", "This is the newest version of the Greg's text editor v.1.01")



root = Tk(className= " Text Editor")

app = GUI()
app.mainloop()