code: def test_add_accumulators_moments(self):
      moments = combiners.SumOfRandomVariablesMoments(
          count=10, expectation=5, variance=50, third_central_moment=1
      )
      acc1 = (None, moments)
      acc2 = (None, moments)
      acc = combiners._merge_partition_selection_accumulators(
          acc1, acc2
      )
  
      # Test that the result has moments.
      probabilities, moments = acc
      self.assertIsNone(probabilities)
      self.assertEqual(20, moments.count)
      self.assertEqual(10, moments.expectation)
      self.assertEqual(100, moments.variance)
      self.assertEqual(2, moments.third_central_moment)
  
      # Test that no type is np.float64
      self.assertTrue(_check_none_are_np_float64(acc))
  
imports: import dataclasses
  import numpy
  from absl.testing import absltest
  from absl.testing import parameterized
  from unittest.mock import patch
  from typing import Tuple
  import pipeline_dp
  from analysis import per_partition_combiners
  from analysis import metrics
  from analysis.tests import common
label_desc: Use image node_id 6 for calling the PartitionSelectionTest obj's underlying member method code with example usage: obj.test_add_accumulators_moments() without return types