code: def caseok_env_changed(self, *, should_exist):
      possibilities = b"PYTHONCASEOK", "PYTHONCASEOK"
      if (
          any(
              x in self.importlib._bootstrap_external._os.environ
              for x in possibilities
          )
          != should_exist
      ):
          self.skipTest(
              "os.environ changes not reflected in _os.environ"
          )
  
imports: import builtins
  import contextlib
  import errno
  import functools
  from importlib import machinery, util, invalidate_caches
  import marshal
  import os
  import os.path
  from test.support import import_helper
  from test.support import os_helper
  import unittest
  import sys
  import tempfile
  import types
label_desc: Use image node_id 1 for calling the CASEOKTestBase obj's underlying member method code with example usage: obj.caseok_env_changed() without return types