code: def test_structures(self):
      WNDPROC = WINFUNCTYPE(c_long, c_int, c_int, c_int, c_int)
  
      def wndproc(hwnd, msg, wParam, lParam):
          return hwnd + msg + wParam + lParam
  
      HINSTANCE = c_int
      HICON = c_int
      HCURSOR = c_int
      LPCTSTR = c_char_p
  
      class WNDCLASS(Structure):
          _fields_ = [
              ("style", c_uint),
              ("lpfnWndProc", WNDPROC),
              ("cbClsExtra", c_int),
              ("cbWndExtra", c_int),
              ("hInstance", HINSTANCE),
              ("hIcon", HICON),
              ("hCursor", HCURSOR),
              ("lpszMenuName", LPCTSTR),
              ("lpszClassName", LPCTSTR),
          ]
  
      wndclass = WNDCLASS()
      wndclass.lpfnWndProc = WNDPROC(wndproc)
  
      WNDPROC_2 = WINFUNCTYPE(c_long, c_int, c_int, c_int, c_int)
  
      self.assertIs(WNDPROC, WNDPROC_2)
      self.assertEqual(wndclass.lpfnWndProc(1, 2, 3, 4), 10)
  
      f = wndclass.lpfnWndProc
  
      del wndclass
      del wndproc
  
      self.assertEqual(f(10, 11, 12, 13), 46)
  
file_path: cpython/Lib/test/test_ctypes/test_funcptr.py
imports: import _ctypes_test
  import ctypes
  import unittest
  from ctypes import CDLL, Structure, CFUNCTYPE, sizeof, _CFuncPtr, c_void_p, c_char_p, c_char, c_int, c_uint, c_long
  from ._support import _CData, PyCFuncPtrType, Py_TPFLAGS_DISALLOW_INSTANTIATION, Py_TPFLAGS_IMMUTABLETYPE
label_desc: Use image node_id 5 for calling the CFuncPtrTestCase obj's underlying member method code with example usage: obj.test_structures() and returns: unknown