code: def test_save(self):
      self.classifier.save(filename="test.file", path=None)
      self.classifier.save(filename="test.file", path="./")
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import logging
  import unittest
  import xgboost
  import numpy
  from art.estimators.classification.xgboost import XGBoostClassifier
  from tests.utils import TestBase, master_seed
label_desc: Use image node_id 4 for calling the TestXGBoostClassifierBoosterSoftprob obj's underlying member method code with example usage: obj.test_save() without return types