code: def test_python_source_files(self):
      for extension in util.py_extensions:
          with self.subTest(extension=extension):
              self.assertTrue(_extension_in_filetypes(extension))
  
file_path: cpython/Lib/idlelib/idle_test/test_iomenu.py
imports: from idlelib import iomenu
  import unittest
  from test.support import requires
  from tkinter import Tk
  from idlelib.editor import EditorWindow
  from idlelib import util
  from idlelib.idle_test.mock_idle import Func
  from tokenize import open, detect_encoding
label_desc: Use image node_id 1 for calling the FiletypesTest obj's underlying member method code with example usage: obj.test_python_source_files() without return types