code: def fit_add_matern_gp_with_dataset(dataset, nu=1.5):
      """Fits an Additive GP with Matern kernels."""
      options = load_options(euclidean_gp_args)
      options.kernel_type = "matern"
      options.matern_nu = nu
      return fit_add_gp_with_dataset(dataset, options)
  
imports: from __future__ import division
  import unittest
  import numpy
  from .euclidean_gp import EuclideanGP, EuclideanGPFitter, euclidean_gp_args
  from .unittest_gp_core import compute_average_prediction_error
  from .unittest_gp_core import gen_gp_test_data
  from ..utils.base_test_class import BaseTestClass, execute_tests
  from ..utils.option_handler import load_options
label_desc: Use image node_id 9 for calling a global function with example usage: fit_add_matern_gp_with_dataset(dataset, nu) and returns: fit_add_gp_with_dataset