code: def test_initial_model(self):
      featurized_data = self.get_data()
      estimator1 = VowpalWabbitClassifier()
  
      model1 = estimator1.fit(featurized_data)
  
      estimator2 = VowpalWabbitClassifier()
      estimator2.setInitialModel(model1.getNativeModel())
  
      model2 = estimator2.fit(featurized_data)
  
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 5 for calling the VowpalWabbitSpec obj's underlying member method code with example usage: obj.test_initial_model() without return types