code: def test_bug1728403(self):
      try:
          f = open(TESTFN, "wb")
          try:
              f.write(b"\xa1")
          finally:
              f.close()
          f = codecs.open(TESTFN, encoding="cp949")
          try:
              self.assertRaises(UnicodeDecodeError, f.read, 2)
          finally:
              f.close()
      finally:
          os_helper.unlink(TESTFN)
  
imports: import _multibytecodec
  import codecs
  import io
  import sys
  import textwrap
  import unittest
  from test import support
  from test.support import os_helper
  from test.support.os_helper import TESTFN
label_desc: Use image node_id 1 for calling the Test_StreamReader obj's underlying member method code with example usage: obj.test_bug1728403() without return types