code: def test_OLS(self):
      diabetes = datasets.load_diabetes()
      estimator = base.StatsModelsRegressor(sm.OLS)
      fitted = estimator.fit(diabetes.data, diabetes.target)
      result = estimator.predict(diabetes.data)
  
      # estimator.score(diabetes.data, diabetes.target)
  
      import statsmodels.regression.linear_model as lm
  
      self.assertIsInstance(fitted, lm.RegressionResultsWrapper)
  
      fitted2 = sm.OLS(diabetes.target, diabetes.data).fit()
      expected = fitted2.predict(diabetes.data)
      self.assert_numpy_array_almost_equal(result, expected)
  
file_path: pandas-ml/pandas_ml/smaccessors/test/test_base.py
imports: import pytest
  import numpy
  import sklearn.datasets
  import statsmodels.api
  import pandas_ml.smaccessors.base
  import pandas_ml.util.testing
label_desc: Use image node_id 2 for calling the TestBaseRegressor obj's underlying member method code with example usage: obj.test_OLS() without return types