code: def test_callback_virtual_func():
      extended = ExtendedVirtClass()
      m.test_callback_virtual_func(extended)
  
imports: import multiprocessing
  import sys
  import threading
  import time
  import pytest
  import env
  from pybind11_tests import gil_scoped
label_desc: Use image node_id 3 for calling a global function with example usage: test_callback_virtual_func() without return types