Button Widget Not Getting Destroyed While Trying To Remove From The Grid

a. Have a scenario where I wanted to remove a button after few clicks.
b. But when the button reaches the last click, its not getting destroyed.
Code as given below:

class test_button:

def __init__(self, master):

    self.master = master

    self.next_button = None



    if not (self.next_button): 

        self.next_button = Button(root, background="orange red", activebackground="orangered3", text="Next Test Config", command=self.next_button_code).grid(row=1, column=1)    



 def next_button_code(self):

     if self.next_button:

         self.next_button.destroy(); self.next_button = None



# Top Local Variables

root = Tk()



# Top Level Default Codes

my_gui = test_button(root)



root.mainloop()