code: def test_tabify_region_event(self, _asktabwidth):
      tabify = self.formatter.tabify_region_event
      text = self.text
      eq = self.assertEqual
  
      text.tag_add("sel", "7.0", "10.0")
      # No tabwidth selected.
      _asktabwidth.return_value = None
      self.assertIsNone(tabify())
  
      _asktabwidth.return_value = 3
      self.assertIsNotNone(tabify())
      eq(
          text.get("7.0", "10.0"),
          ("\n\t def compare(self):\n\t\t  if a > b:\n"),
      )
  
imports: from idlelib import format
  import unittest
  from unittest import mock
  from test.support import requires
  from tkinter import Tk, Text
  from idlelib.editor import EditorWindow
  from idlelib.idle_test.mock_idle import Editor
label_desc: Use image node_id 11 for calling the FormatRegionTest obj's underlying member method code with example usage: obj.test_tabify_region_event(_asktabwidth) without return types