code: def test_default_configuration(self):
      transformation, original = _test_preprocessing(
          Densifier, make_sparse=True
      )
      self.assertIsInstance(transformation, np.ndarray)
      self.assertEqual(transformation.shape, original.shape)
      self.assertIsInstance(transformation, np.ndarray)
  
imports: import numpy
  from autosklearn.pipeline.components.feature_preprocessing.densifier import Densifier
  from autosklearn.pipeline.util import PreprocessingTestCase, _test_preprocessing
label_desc: Use image node_id 1 for calling the DensifierComponentTest obj's underlying member method code with example usage: obj.test_default_configuration() without return types