code: def test_linear(self):
      X = np.atleast_2d([1.0, 3.0, 5.0, 6.0, 7.0, 8.0]).T
      df = pdml.ModelFrame(X)
  
      result = df.gaussian_process.regression_models.linear()
      expected = gp.regression_models.linear(X)
      self.assert_numpy_array_almost_equal(result, expected)
  
file_path: pandas-ml/pandas_ml/skaccessors/test/test_gaussian_process.py
imports: import numpy
  import sklearn.gaussian_process
  import pandas_ml
  import pandas_ml.util.testing
label_desc: Use image node_id 5 for calling the TestGaussianProcess obj's underlying member method code with example usage: obj.test_linear() without return types