[Tkinter] should not be getting this exception...confused

[MrP]

This is the whole code

import tkinter as tk


class Buttons:
    def __init(self, master):
        self.master = master
        self.frame = tk.Frame(self.master)
        self.b1 = tk.Button(self.master, text="Button1", command=self.display)
        self.b2 = tk.Button(self.master, text="Button2", command=self.new_window)
        self.b1.pack()
        self.b2.pack()
        self.frame.pack()
        
    def display(self):
        print("Hello Button1")
        
    def new_window(self):
        self.master.withdraw()
        self.newWindow = tk.Toplevel(self.master)
        
        
class Buttons1():
    def __init__(self, master):
        self.master = master
        self.frame = tk.Frame(self.master)
        self.frame.pack()
        
        
if __name__ == '__main__':
    root = tk.Tk()
    b = Buttons(root)
    root.mainloop()