code: def test_generate_pipeline_code_2():
      """Assert that generate_pipeline_code() returns the correct code given a specific pipeline with two CombineDFs."""
  
      pipeline = [
          "KNeighborsClassifier",
          [
              "CombineDFs",
              [
                  "GradientBoostingClassifier",
                  "input_matrix",
                  38.0,
                  5,
                  5,
                  5,
                  0.05,
                  0.5,
              ],
              [
                  "CombineDFs",
                  ["MinMaxScaler", "input_matrix"],
                  ["ZeroCount", ["MaxAbsScaler", "input_matrix"]],
              ],
          ],
          18,
          "uniform",
          2,
      ]
  
      expected_code = """make_pipeline(
      make_union(
          StackingEstimator(estimator=GradientBoostingClassifier(learning_rate=38.0, max_depth=5, max_features=5, min_samples_leaf=5, min_samples_split=0.05, n_estimators=0.5)),
          make_union(
              MinMaxScaler(),
              make_pipeline(
                  MaxAbsScaler(),
                  ZeroCount()
              )
          )
      ),
      KNeighborsClassifier(n_neighbors=18, p="uniform", weights=2)
  )"""
  
      assert expected_code == generate_pipeline_code(
          pipeline, tpot_obj.operators
      )
  
imports: from tqdm import tqdm
  import numpy
  from os import remove, path
  from tpot import TPOTClassifier, TPOTRegressor
  from tpot.export_utils import export_pipeline, generate_import_code, _indent, generate_pipeline_code, get_by_name, set_param_recursive
  from tpot.operator_utils import TPOTOperatorClassFactory
  from tpot.config.classifier import classifier_config_dict
  from sklearn.datasets import load_digits
  from sklearn.model_selection import train_test_split
  from deap import creator
  from nose.tools import assert_raises, assert_equal, nottest
label_desc: Use image node_id 5 for calling a global function with example usage: test_generate_pipeline_code_2() without return types