code: def test_default_threads_OpenMP(self):
      # unset environment variables if they were defined
      os.environ.pop("PYFFTW_NUM_THREADS", None)
      os.environ.pop("OMP_NUM_THREADS", None)
  
      # defaults to single-threaded if neither variable is defined
      config._reload_config()
      assert_equal(config.NUM_THREADS, 1)
  
      # load default from OMP_NUM_THREADS environment variable
      os.environ["OMP_NUM_THREADS"] = "2"
      config._reload_config()
      assert_equal(config.NUM_THREADS, 2)
  
      # PYFFTW_NUM_THREADS overrides OMP_NUM_THREADS when both are defined
      os.environ["PYFFTW_NUM_THREADS"] = "4"
      config._reload_config()
      assert_equal(config.NUM_THREADS, 4)
  
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 4 for calling the ConfigTest obj's underlying member method code with example usage: obj.test_default_threads_OpenMP() without return types