How to call function of main code in an Imported module?

Question

Can an imported module make the Main module call a function? I created a sequence diagram and I have a barebones code example of what I mean:

main:

import test2

def function():
    do sth

test2:

import tkinter as tk

window  = tk.Tk()
test = tk.Button(master = window, text = "hdsd", command = # call function of main program)
test.grid(row = 0, column = 0)
window.mainloop()