class_docstr: Test the Linear kernel.
class_docstr_tok: ["Test","the","Linear","kernel","."]
code: def testIsPolynomial(self):
      # Linear kernel is subclass of Polynomial kernel
      self.assertIsInstance(polynomial.Linear(), polynomial.Polynomial)
  
imports: from absl.testing import parameterized
  import numpy
  import tensorflow.compat.v2
  from tensorflow_probability.python.internal import test_util
  from tensorflow_probability.python.math import gradient
  from tensorflow_probability.python.math.psd_kernels import polynomial
label_desc: Use image node_id 1 for calling the LinearTest obj's underlying member method code with example usage: obj.testIsPolynomial() without return types