code: def test_cov_nw_no_demean(self):
      y = self.inflation
      simple_cov = cov_nw(y, lags=0, demean=False)
      assert_almost_equal(y.dot(y) / y.shape[0], simple_cov)
  
file_path: arch/arch/tests/utility/test_cov.py
imports: from __future__ import annotations
  from arch.compat.statsmodels import dataset_loader
  from numpy import diff, log
  from numpy.random import RandomState
  from numpy.testing import assert_almost_equal
  import pytest
  from statsmodels.datasets import macrodata
  from arch.utility import cov_nw
label_desc: Use image node_id 4 for calling the TestVarNW obj's underlying member method code with example usage: obj.test_cov_nw_no_demean() without return types