code: def test_select_partitions_calls_select_partitions_with_correct_params(
      self, mock_aggregate
  ):
      # Arrange
      dist_data = PrivateRDDTest.sc.parallelize(
          [(1, "pk1"), (2, "pk2")]
      )
      expected_result_partitions = ["pk1", "pk2"]
      mock_aggregate.return_value = PrivateRDDTest.sc.parallelize(
          expected_result_partitions
      )
      budget_accountant = budget_accounting.NaiveBudgetAccountant(
          total_epsilon=1, total_delta=0.01
      )
      max_partitions_contributed = 2
  
      def privacy_id_extractor(x):
          return x[0]
  
      def partition_extractor(x):
          return {x[1]}
  
      # Act
      prdd = private_spark.make_private(
          dist_data, budget_accountant, privacy_id_extractor
      )
  
      select_partitions_params = agg.SelectPartitionsParams(
          max_partitions_contributed=max_partitions_contributed
      )
      actual_result = prdd.select_partitions(
          select_partitions_params, partition_extractor
      )
  
      # Assert
      mock_aggregate.assert_called_once()
      actual_args = mock_aggregate.call_args[0]
      actual_rdd = actual_args[0].collect()
      actual_select_partition_params = actual_args[1]
  
      self.assertListEqual(
          actual_rdd, [(1, (1, "pk1")), (2, (2, "pk2"))]
      )
  
      self.assertEqual(
          actual_select_partition_params.max_partitions_contributed,
          max_partitions_contributed,
      )
      self.assertEqual(
          actual_result.collect(), expected_result_partitions
      )
  
imports: import pyspark
  from pyspark import SparkContext
  from absl.testing import parameterized
  from unittest.mock import patch
  import unittest
  import sys
  import collections
  import pipeline_dp
  from pipeline_dp import aggregate_params
  from pipeline_dp import budget_accounting, private_spark
label_desc: Use image node_id 21 for calling the PrivateRDDTest obj's underlying member method code with example usage: obj.test_select_partitions_calls_select_partitions_with_correct_params(mock_aggregate) and returns: x, unknown