code: def test_mainloop(self):
      self.assertRaises(RuntimeError, tkinter.mainloop)
      root = tkinter.Tk()
      root.after_idle(root.quit)
      tkinter.mainloop()
      root.destroy()
      tkinter.NoDefaultRoot()
      self.assertRaises(RuntimeError, tkinter.mainloop)
  
imports: import functools
  import unittest
  import tkinter
  from tkinter import TclError
  import enum
  from test import support
  from test.test_tkinter.support import AbstractTkTest, AbstractDefaultRootTest, requires_tk
label_desc: Use image node_id 4 for calling the DefaultRootTest obj's underlying member method code with example usage: obj.test_mainloop() without return types