code: def test_precision_formula(self):
      m = BetaModel.from_formula(
          self.model,
          methylation,
          exog_precision_formula="~ age",
          link_precision=links.Identity(),
      )
      rslt = m.fit()
      assert_close(rslt.params, self.meth_fit.params, 1e-10)
      assert isinstance(rslt.params, pd.Series)
  
      with pytest.warns(ValueWarning, match="unknown kwargs"):
          BetaModel.from_formula(
              self.model,
              methylation,
              exog_precision_formula="~ age",
              link_precision=links.Identity(),
              junk=False,
          )
  
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 6 for calling the TestBetaModel obj's underlying member method code with example usage: obj.test_precision_formula() without return types