code: def test_medium_dataset(self):
      m = ExternalMerger(self.agg, 20)
      m.mergeValues(self.data)
      self.assertTrue(m.spills >= 1)
      self.assertEqual(
          sum(sum(v) for k, v in m.items()), sum(range(self.N))
      )
  
      m = ExternalMerger(self.agg, 10)
      m.mergeCombiners(
          map(lambda x_y2: (x_y2[0], [x_y2[1]]), self.data * 3)
      )
      self.assertTrue(m.spills >= 1)
      self.assertEqual(
          sum(sum(v) for k, v in m.items()), sum(range(self.N)) * 3
      )
  
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 3 for calling the MergerTests obj's underlying member method code with example usage: obj.test_medium_dataset() without return types