code: def test_oas(self):
      iris = datasets.load_iris()
      df = pdml.ModelFrame(iris)
  
      result = df.covariance.oas()
      expected = covariance.oas(iris.data)
  
      self.assertEqual(len(result), 2)
  
      self.assertIsInstance(result[0], pdml.ModelFrame)
      tm.assert_index_equal(result[0].index, df.data.columns)
      tm.assert_index_equal(result[0].columns, df.data.columns)
      self.assert_numpy_array_almost_equal(
          result[0].values, expected[0]
      )
  
      self.assert_numpy_array_almost_equal(result[1], expected[1])
  
file_path: pandas-ml/pandas_ml/skaccessors/test/test_covariance.py
imports: import pytest
  import sklearn.datasets
  import sklearn.covariance
  import pandas_ml
  import pandas_ml.util.testing
label_desc: Use image node_id 4 for calling the TestCovariance obj's underlying member method code with example usage: obj.test_oas() without return types