code: def test_trailing_counter(self):
      store = array.array("b", b" " * 100)
  
      # format lists containing only count spec should result in an error
      self.assertRaises(struct.error, struct.pack, "12345")
      self.assertRaises(struct.error, struct.unpack, "12345", b"")
      self.assertRaises(
          struct.error, struct.pack_into, "12345", store, 0
      )
      self.assertRaises(
          struct.error, struct.unpack_from, "12345", store, 0
      )
  
      # Format lists with trailing count spec should result in an error
      self.assertRaises(struct.error, struct.pack, "c12345", "x")
      self.assertRaises(struct.error, struct.unpack, "c12345", b"x")
      self.assertRaises(
          struct.error, struct.pack_into, "c12345", store, 0, "x"
      )
      self.assertRaises(
          struct.error, struct.unpack_from, "c12345", store, 0
      )
  
      # Mixed format tests
      self.assertRaises(
          struct.error, struct.pack, "14s42", "spam and eggs"
      )
      self.assertRaises(
          struct.error, struct.unpack, "14s42", b"spam and eggs"
      )
      self.assertRaises(
          struct.error,
          struct.pack_into,
          "14s42",
          store,
          0,
          "spam and eggs",
      )
      self.assertRaises(
          struct.error, struct.unpack_from, "14s42", store, 0
      )
  
imports: from collections import abc
  import array
  import gc
  import math
  import operator
  import unittest
  import struct
  import sys
  import weakref
  from test import support
  from test.support import import_helper
  from test.support.script_helper import assert_python_ok
label_desc: Use image node_id 17 for calling the StructTest obj's underlying member method code with example usage: obj.test_trailing_counter() without return types