code: def test_boston_housing_simple_regression(self):
      self._train_convert_evaluate_assert()
  
imports: import itertools
  import unittest
  import pandas
  import pytest
  from coremltools._deps import _HAS_SKLEARN, _HAS_XGBOOST
  from coremltools.models.utils import _is_macos, _macos_version, evaluate_regressor
label_desc: Use image node_id 4 for calling the GradientBoostingRegressorBostonHousingScikitNumericTest obj's underlying member method code with example usage: obj.test_boston_housing_simple_regression() without return types