code: def test_simple_aggregator_with_medium_dataset(self):
      # SPARK-39179: Test Simple aggregator
      agg = SimpleAggregator(lambda x, y: x + y)
      m = ExternalMerger(agg, 20)
      m.mergeValues(self.data)
      self.assertTrue(m.spills >= 1)
      self.assertEqual(sum(v for k, v in m.items()), sum(range(self.N)))
  
imports: import random
  import unittest
  import tempfile
  import os
  from py4j.protocol import Py4JJavaError
  from pyspark import shuffle, CPickleSerializer, SparkConf, SparkContext
  from pyspark.shuffle import Aggregator, ExternalMerger, ExternalSorter, SimpleAggregator, Merger, ExternalGroupBy
label_desc: Use image node_id 5 for calling the MergerTests obj's underlying member method code with example usage: obj.test_simple_aggregator_with_medium_dataset() without return types