code: def setup_class(cls):
      cls.rng = RandomState(12345)
      cls.cpi = log(dataset_loader(macrodata)["cpi"])
      cls.inflation = diff(cls.cpi)
  
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 1 for calling the TestVarNW obj's underlying member method code with example usage: obj.setup_class(cls) without return types