code: def test_results(self):
      unexp, exp, gap = self.zero_model.params
      unexp_std, exp_std = self.zero_model.std
      zero_params_stata_results = np.array(
          [-162.9978, 321.7482, 158.75044]
      )
      zero_std_stata_results = np.array([668.1512, 653.10389])
  
      np.testing.assert_almost_equal(
          unexp, zero_params_stata_results[0], 3
      )
      np.testing.assert_almost_equal(
          exp, zero_params_stata_results[1], 3
      )
      np.testing.assert_almost_equal(
          gap, zero_params_stata_results[2], 3
      )
  
      np.testing.assert_almost_equal(
          unexp_std, zero_std_stata_results[0], 3
      )
      np.testing.assert_almost_equal(
          exp_std, zero_std_stata_results[1], 3
      )
  
imports: import numpy
  from statsmodels.datasets.ccard.data import load_pandas
  from statsmodels.stats.oaxaca import OaxacaBlinder
  from statsmodels.tools.tools import add_constant
label_desc: Use image node_id 2 for calling the TestZeroModel obj's underlying member method code with example usage: obj.test_results() without return types