code: def test_fields(self):
      # test the offset and size attributes of Structure/Union fields.
      class X(Structure):
          _fields_ = [("x", c_int), ("y", c_char)]
  
      self.assertEqual(X.x.offset, 0)
      self.assertEqual(X.x.size, sizeof(c_int))
  
      self.assertEqual(X.y.offset, sizeof(c_int))
      self.assertEqual(X.y.size, sizeof(c_char))
  
      # readonly
      self.assertRaises(
          (TypeError, AttributeError), setattr, X.x, "offset", 92
      )
      self.assertRaises(
          (TypeError, AttributeError), setattr, X.x, "size", 92
      )
  
      class X(Union):
          _fields_ = [("x", c_int), ("y", c_char)]
  
      self.assertEqual(X.x.offset, 0)
      self.assertEqual(X.x.size, sizeof(c_int))
  
      self.assertEqual(X.y.offset, 0)
      self.assertEqual(X.y.size, sizeof(c_char))
  
      # readonly
      self.assertRaises(
          (TypeError, AttributeError), setattr, X.x, "offset", 92
      )
      self.assertRaises(
          (TypeError, AttributeError), setattr, X.x, "size", 92
      )
  
imports: import _ctypes_test
  from platform import architecture
  import struct
  import sys
  import unittest
  from ctypes import CDLL, Array, Structure, Union, POINTER, sizeof, byref, alignment, c_void_p, c_char, c_wchar, c_byte, c_ubyte, c_uint8, c_uint16, c_uint32, c_short, c_ushort, c_int, c_uint, c_long, c_ulong, c_longlong, c_ulonglong, c_float, c_double
  from ctypes.util import find_library
  from struct import calcsize
  from collections import namedtuple
  from test import support
  from ._support import _CData, PyCStructType, Py_TPFLAGS_DISALLOW_INSTANTIATION, Py_TPFLAGS_IMMUTABLETYPE
label_desc: Use image node_id 7 for calling the StructureTestCase obj's underlying member method code with example usage: obj.test_fields() without return types