code: def test_void(self):
      self._dll.tv_i.restype = None
      self._dll.tv_i.argtypes = (c_int,)
      self.assertEqual(self._dll.tv_i(42), None)
      self.assertEqual(self.S(), 42)
      self.assertEqual(self._dll.tv_i(-42), None)
      self.assertEqual(self.S(), -42)
  
imports: import unittest
  from ctypes import *
  from ctypes.test import need_symbol
  import _ctypes_test
label_desc: Use image node_id 30 for calling the CFunctions obj's underlying member method code with example usage: obj.test_void() without return types