code: def tearDown(self):
      # restore original environment variables values
      for key in self.env_keys:
          val = self.orig_env[key]
          if val is None:
              os.environ.pop(key, None)
          else:
              os.environ[key] = val
      return
  
file_path: py-fftw/tests/test_pyfftw_config.py
imports: from pyfftw import config, _threading_type
  from .test_pyfftw_base import run_test_suites
  import unittest
  import os
  from numpy.testing import assert_equal
label_desc: Use image node_id 2 for calling the ConfigTest obj's underlying member method code with example usage: obj.tearDown() without return types