class_docstr: Class to help protect the environment variable properly.  Can be used as
  a context manager.
class_docstr_tok: ["Class","to","help","protect","the","environment","variable","properly",".","Can","be","used","as","a","context","manager","."]
code: def __exit__(self, *ignore_exc):
      for k, v in self._changed.items():
          if v is None:
              if k in self._environ:
                  del self._environ[k]
          else:
              self._environ[k] = v
      os.environ = self._environ
  
imports: import collections.abc
  import contextlib
  import errno
  import os
  import re
  import stat
  import string
  import sys
  import time
  import unittest
  import warnings
  from test import support
label_desc: Use image node_id 12 for calling the EnvironmentVarGuard obj's underlying member method code with example usage: obj.__exit__() without return types