docstr: Verify that BarrierTaskContext.get() should only works in a barrier stage.
docstr_tok: ["Verify","that","BarrierTaskContext.get","(",")","should","only","works","in","a","barrier","stage","."]
code: def test_barrier_context_get(self):
      """
      Verify that BarrierTaskContext.get() should only works in a barrier stage.
      """
      rdd = self.sc.parallelize(range(10), 4)
  
      def f(iterator):
          try:
              taskContext = BarrierTaskContext.get()
          except Exception:
              yield -1
          else:
              yield taskContext.partitionId()
  
      # for normal stage
      result1 = rdd.mapPartitions(f).collect()
      self.assertTrue(result1 == [-1, -1, -1, -1])
      # for barrier stage
      result2 = rdd.barrier().mapPartitions(f).collect()
      self.assertTrue(result2 == [0, 1, 2, 3])
  
imports: import os
  import random
  import stat
  import sys
  import tempfile
  import time
  import unittest
  from pyspark import SparkConf, SparkContext, TaskContext, BarrierTaskContext
  from pyspark.testing.utils import PySparkTestCase, SPARK_HOME, eventually
label_desc: Use image node_id 12 for calling the TaskContextTests obj's underlying member method code with example usage: obj.test_barrier_context_get() without return types