tkinter dialogue

from tkinter import *
from tkinter.filedialog import askopenfilename
from tkinter.messagebox import showerror
from tkinter.messagebox import askyesno
from tkinter.messagebox import askyesno
from tkinter.messagebox import showwarning

def answer():
    showerror("Answer", "Sorry, no answer available")

def callback():
    if askyesno('Verify', 'Really quit?'):
        showwarning('Yes', 'Not yet implemented')
 
    else:
        showinfo('No', 'Quit has been cancelled')

Button(text='Quit', command=callback).pack(fill=X)
Button(text='Answer', command=answer).pack(fill=X)
mainloop()