code: def test_to_dense(self):
      combiner = self._create_combiner()
      sparse_acc = ([1, 3], [10, 20], [100, 200])
      dense = combiner._to_dense(sparse_acc)
      num_privacy_ids, (count_acc,) = dense
      self.assertEqual(2, num_privacy_ids)
      self.assertSequenceEqual((4, 0, -1.0, -2.98, 0.0298), count_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 4 for calling the UtilityAnalysisCompoundCombinerTest obj's underlying member method code with example usage: obj.test_to_dense() without return types