code: def setup_class(cls):
      cls.rng = RandomState(12345)
      cls.t = 1000
      cls.resid = cls.rng.standard_normal(cls.t) * np.sqrt(10)
  
imports: import numpy
  from numpy.random import RandomState
  from numpy.testing import assert_allclose
  import pandas
  import pytest
  from arch.univariate import arch_model
  from arch.univariate.distribution import Normal, StudentsT
  from arch.univariate.mean import ConstantMean
  from arch.univariate.volatility import APARCH, EGARCH, FIGARCH, GARCH, HARCH, BootstrapRng, ConstantVariance, EWMAVariance, FixedVariance, MIDASHyperbolic, RiskMetrics2006
label_desc: Use image node_id 1 for calling the TestVarianceForecasts obj's underlying member method code with example usage: obj.setup_class(cls) without return types