code: def setup_class(cls):
      super().setup_class()
      nobs = 10000
      np.random.seed(987689)
      x = np.random.randn(nobs, 3)
      cls.exog = pd.DataFrame(x, columns=["A", "B", "C"])
      cls.xf = pd.DataFrame(
          0.25 * np.ones((2, 3)), columns=cls.exog.columns
      )
      cls.reduction_factor = 0.5
  
imports: from statsmodels.compat.pandas import assert_series_equal
  from io import BytesIO
  import pickle
  import numpy
  import pandas
  import statsmodels.api
label_desc: Use image node_id 1 for calling the TestPickleFormula obj's underlying member method code with example usage: obj.setup_class(cls) without return types