code: def setup_method(self):
      x = self.exog
      np.random.seed(123)
      y = x.sum(1) + np.random.randn(x.shape[0])
      y = pd.Series(y, name="Y")
      X = self.exog.copy()
      X["Y"] = y
      self.results = sm.OLS.from_formula("Y ~ A + B + C", data=X).fit()
  
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 2 for calling the TestPickleFormula obj's underlying member method code with example usage: obj.setup_method() without return types