code: def test_unregister(self):
      self.assertIsNone(self.redir.unregister("invalid operation name"))
      self.assertEqual(self.redir.unregister("insert"), self.func)
      self.assertNotIn("insert", self.redir._operations)
      self.assertNotIn("insert", self.text.__dict__)
  
imports: from idlelib.redirector import WidgetRedirector
  import unittest
  from test.support import requires
  from tkinter import Tk, Text, TclError
  from idlelib.idle_test.mock_idle import Func
label_desc: Use image node_id 8 for calling the WidgetRedirectorTest obj's underlying member method code with example usage: obj.test_unregister() without return types