code: def test_k_best_chi2(self):
      X, y = load_digits(return_X_y=True)
      selector = SelectKBest(chi2, k=20)
      selector.fit_transform(X, y)
      data_tensor = torch.from_numpy(X)
  
      torch_model = hummingbird.ml.convert(selector, "torch")
  
      self.assertIsNotNone(torch_model)
      np.testing.assert_allclose(
          selector.transform(X),
          torch_model.transform(data_tensor),
          rtol=1e-06,
          atol=1e-06,
      )
  
file_path: hummingbird/tests/test_sklearn_array_feature_extractor_converter.py
imports: import unittest
  import warnings
  import numpy
  import torch
  from sklearn.feature_selection import chi2, mutual_info_classif, SelectKBest, SelectPercentile, VarianceThreshold
  from sklearn.datasets import load_digits
  import hummingbird.ml
label_desc: Use image node_id 5 for calling the TestSklearnArrayFeatureExtractor obj's underlying member method code with example usage: obj.test_k_best_chi2() without return types