code: def test_py4j_str(self):
      with self.assertRaises(Py4JJavaError) as context:
          # This attempts java.lang.String(null) which throws an NPE.
          self.sc._jvm.java.lang.String(None)
  
      self.assertTrue("NullPointerException" in str(context.exception))
  
imports: import os
  import unittest
  from py4j.protocol import Py4JJavaError
  from pyspark import keyword_only
  from pyspark.util import _parse_memory
  from pyspark.loose_version import LooseVersion
  from pyspark.testing.utils import PySparkTestCase, eventually
  from pyspark.find_spark_home import _find_spark_home
label_desc: Use image node_id 1 for calling the UtilTests obj's underlying member method code with example usage: obj.test_py4j_str() without return types