code: def save_model(self, estimator):
      model = estimator.fit(self.get_data())
  
      # write model to file and validate it's there
      with tempfile.TemporaryDirectory() as tmpdirname:
          modelFile = "{}/model".format(tmpdirname)
  
          model.saveNativeModel(modelFile)
  
          self.assertTrue(os.stat(modelFile).st_size > 0)
  
file_path: SynapseML/vw/src/test/python/synapsemltest/vw/test_vw.py
imports: import os
  import unittest
  import tempfile
  import pyspark
  from synapse.ml.vw.VowpalWabbitClassifier import VowpalWabbitClassifier
  from synapse.ml.vw.VowpalWabbitRegressor import VowpalWabbitRegressor
  from synapse.ml.vw.VowpalWabbitFeaturizer import VowpalWabbitFeaturizer
  from pyspark.sql.types import *
  from synapsemltest.spark import *
label_desc: Use image node_id 2 for calling the VowpalWabbitSpec obj's underlying member method code with example usage: obj.save_model(estimator) without return types