code: def test_nonstationary_series_variance():
      # See `test_nonstationary_series`. This part of the test has been broken
      # out as an xfail because we compute a different estimate of the variance
      # from stats::ar.yw, but keeping the test in case we want to also implement
      # that variance estimate in the future.
      endog = np.arange(1, 12) * 1.0
      res, _ = durbin_levinson(endog, 2, demean=False)
  
      desired_sigma2 = 15.36526603
      assert_allclose(res[2].sigma2, desired_sigma2)
  
file_path: statsmodels/statsmodels/tsa/arima/estimators/tests/test_durbin_levinson.py
imports: import numpy
  import pytest
  from numpy.testing import assert_allclose, assert_raises
  from statsmodels.tsa.innovations.arma_innovations import arma_innovations
  from statsmodels.tsa.arima.datasets.brockwell_davis_2002 import dowj, lake
  from statsmodels.tsa.arima.estimators.durbin_levinson import durbin_levinson
label_desc: Use image node_id 5 for calling a global function with example usage: test_nonstationary_series_variance() without return types