code: def test_ignore_retval(self):
      # Test if the return value of a callback is ignored
      # if restype is None
      proto = CFUNCTYPE(None)
  
      def func():
          return (1, "abc", None)
  
      cb = proto(func)
      self.assertEqual(None, cb())
  
file_path: cpython/Lib/test/test_ctypes/test_simplesubclasses.py
imports: import unittest
  from ctypes import Structure, CFUNCTYPE, c_int, _SimpleCData
  from ._support import _CData, PyCSimpleType, Py_TPFLAGS_DISALLOW_INSTANTIATION, Py_TPFLAGS_IMMUTABLETYPE
label_desc: Use image node_id 4 for calling the Test obj's underlying member method code with example usage: obj.test_ignore_retval() and returns: int,  str,  None