code: def test_custom_e2e_combiners(
      self, mock_create_standard_combiners, mock_create_custom_combiners
  ):
      engine = self._create_dp_engine_default()
  
      custom_combiner = pipeline_dp.combiners.CustomCombiner()
  
      col = [1, 2, 3]
      params = pipeline_dp.AggregateParams(
          max_partitions_contributed=1,
          max_contributions_per_partition=1,
          min_value=0,
          max_value=1,
          metrics=None,
          custom_combiners=[custom_combiner],
      )
  
      data_extractors = self._get_default_extractors()
  
      engine.aggregate(col, params, data_extractors)
      mock_create_custom_combiners.assert_called_once()
      mock_create_standard_combiners.assert_not_called()
  
imports: import sys
  import unittest
  from typing import List, Optional, Tuple
  from unittest.mock import patch
  import numpy
  import apache_beam
  import apache_beam.testing.test_pipeline
  import apache_beam.testing.util
  import pydp.algorithms.partition_selection
  from absl.testing import absltest
  from absl.testing import parameterized
  import pipeline_dp
  from pipeline_dp import aggregate_params
  from pipeline_dp import budget_accounting
  from pipeline_dp import dp_computations
  from pipeline_dp.budget_accounting import NaiveBudgetAccountant
  from pipeline_dp.pipeline_backend import PipelineBackend
  from pipeline_dp.pipeline_functions import collect_to_container
  from pipeline_dp.report_generator import ReportGenerator
label_desc: Use image node_id 38 for calling the DpEngineTest obj's underlying member method code with example usage: obj.test_custom_e2e_combiners(mock_create_standard_combiners, mock_create_custom_combiners) without return types