code: def test_chi2(self):
      iris = datasets.load_iris()
      df = pdml.ModelFrame(iris)
  
      result = df.feature_selection.chi2()
      expected = fs.chi2(iris.data, iris.target)
  
      self.assertEqual(len(result), 2)
      self.assert_numpy_array_almost_equal(result[0], expected[0])
      self.assert_numpy_array_almost_equal(result[1], expected[1])
  
file_path: pandas-ml/pandas_ml/skaccessors/test/test_feature_selection.py
imports: import pytest
  import sklearn.datasets
  import sklearn.feature_selection
  import pandas_ml
  import pandas_ml.util.testing
label_desc: Use image node_id 2 for calling the TestFeatureSelection obj's underlying member method code with example usage: obj.test_chi2() without return types