code: def setup_class(cls):
      super().setup_class()  # initialize DGP
  
      y, x, exog = cls.y, cls.x, cls.exog
  
      # use order = 3 in regression
      pmod = smoothers.PolySmoother(3, x)
      # pmod.fit(y)  #no return
      pmod.smooth(y)  # no return, use alias for fit
  
      cls.res_ps = pmod
      cls.res2 = OLS(y, exog[:, : 3 + 1]).fit()
  
imports: import numpy
  from numpy.testing import assert_almost_equal, assert_equal
  from statsmodels.sandbox.nonparametric import smoothers
  from statsmodels.regression.linear_model import OLS, WLS
label_desc: Use image node_id 1 for calling the TestPolySmoother2 obj's underlying member method code with example usage: obj.setup_class(cls) without return types