[Python] I can't seem to get a function in one class to properly call a function in another...

I am having trouble getting this text box to print text when the button from Class3 is pressed. If I call the same function from Class2 then everything is fine. But from Class 3 not so much. I can still call the function (It even prints to the console) But it does not change the Text window. Can't figure out what I am missing. I am still learning classes in python so having trouble phrasing my questions online to get the desired results.

import tkinter as tk

def mainGUI():
app = Class1()
app.mainloop()


class Class1(tk.Tk):
def __init__(self):
super().__init__()

self.title("test")
frame1 = Class2(self)
frame1.pack()
frame2 = Class3(self)
frame2.pack()


class Class2(tk.Frame):
def __init__(self, parent):
super().__init__(parent)

button1 = tk.Button(self, text='Class2 Button', command=self.doStuff)
button1.pack()

self.text_box = tk.Text(self)
self.text_box.pack()

def doStuff(self):
self.text_box.insert(tk.END, "You Pushed the button!\n")
print("I can print to console though")


class Class3(tk.Frame):
def __init__(self, parent):
super().__init__(parent)

button2 = tk.Button(self, text='Class3 Button', command=Class2(parent).doStuff)
button2.pack()

mainGUI()

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