code: def setup_class(cls):
      model = "I(food/income) ~ income + persons"
      cls.income_fit = BetaModel.from_formula(model, income).fit()
  
      model = cls.model = "methylation ~ gender + CpG"
      Z = cls.Z = patsy.dmatrix("~ age", methylation)
      mod = BetaModel.from_formula(
          model,
          methylation,
          exog_precision=Z,
          link_precision=links.Identity(),
      )
      cls.meth_fit = mod.fit()
      mod = BetaModel.from_formula(
          model,
          methylation,
          exog_precision=Z,
          link_precision=links.Log(),
      )
      cls.meth_log_fit = mod.fit()
  
imports: import io
  import os
  import pytest
  import numpy
  from numpy.testing import assert_allclose, assert_equal
  import pandas
  import patsy
  from statsmodels.api import families
  from statsmodels.tools.sm_exceptions import ValueWarning
  from statsmodels.othermod.betareg import BetaModel
  from .results import results_betareg
label_desc: Use image node_id 1 for calling the TestBetaModel obj's underlying member method code with example usage: obj.setup_class(cls) without return types