code: def _kernel_type(
      self,
      amplitude=None,
      length_scale=None,
      feature_ndims=1,
      inverse_length_scale=None,
      validate_args=None,
      df=None,
  ):
      # Make sure tests work for scalar DF. Non-scalar DF is handled below.
      if df is None:
          df = np.pi
      return matern.GeneralizedMatern(
          df=df,
          amplitude=amplitude,
          length_scale=length_scale,
          inverse_length_scale=inverse_length_scale,
          feature_ndims=feature_ndims,
          validate_args=validate_args,
      )
  
imports: from absl.testing import parameterized
  import numpy
  import scipy.special
  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 matern
label_desc: Use image node_id 1 for calling the GeneralizedMaternTest obj's underlying member method code with example usage: obj._kernel_type(amplitude, length_scale, feature_ndims, inverse_length_scale, validate_args, df) and returns: matern