code: def test_get_best_index():
      """Tests `get_best_index`"""
      results = {
          "mean_test_score": np.array([1.0, 3.0, 2.0]),
          "mean_test_MSE": np.array([3.0, 1.0, -2.0]),
      }
      assert get_best_index(results) == 0
      assert (
          get_best_index(
              results=results, metric="MSE", greater_is_better=True
          )
          == 0
      )
      assert (
          get_best_index(
              results=results, metric="MSE", greater_is_better=False
          )
          == 2
      )
  
imports: import sys
  import warnings
  from functools import partial
  import numpy
  import pandas
  import pytest
  from scipy.stats import randint
  from sklearn.metrics import mean_absolute_error
  from sklearn.metrics import mean_squared_error
  from sklearn.metrics import median_absolute_error
  from sklearn.pipeline import Pipeline
  from testfixtures import LogCapture
  from greykite.common import constants
  from greykite.common.constants import FRACTION_OUTSIDE_TOLERANCE
  from greykite.common.constants import LOGGER_NAME
  from greykite.common.evaluation import EvaluationMetricEnum
  from greykite.common.evaluation import add_preaggregation_to_scorer
  from greykite.common.evaluation import fraction_outside_tolerance
  from greykite.common.python_utils import assert_equal
  from greykite.common.testing_utils import assert_eval_function_equal
  from greykite.common.testing_utils import generate_df_for_tests
  from greykite.common.testing_utils import generate_df_with_reg_for_tests
  from greykite.framework.constants import CUSTOM_SCORE_FUNC_NAME
  from greykite.framework.constants import CV_REPORT_METRICS_ALL
  from greykite.framework.constants import FRACTION_OUTSIDE_TOLERANCE_NAME
  from greykite.framework.pipeline.utils import get_basic_pipeline
  from greykite.framework.pipeline.utils import get_best_index
  from greykite.framework.pipeline.utils import get_default_time_parameters
  from greykite.framework.pipeline.utils import get_forecast
  from greykite.framework.pipeline.utils import get_hyperparameter_searcher
  from greykite.framework.pipeline.utils import get_score_func_with_aggregation
  from greykite.framework.pipeline.utils import get_scoring_and_refit
  from greykite.framework.utils.framework_testing_utils import assert_proper_grid_search
  from greykite.framework.utils.framework_testing_utils import assert_refit
  from greykite.framework.utils.framework_testing_utils import assert_scoring
  from greykite.sklearn.cross_validation import RollingTimeSeriesSplit
  from greykite.sklearn.estimator.null_model import DummyEstimator
  from greykite.sklearn.estimator.prophet_estimator import ProphetEstimator
  from greykite.sklearn.estimator.silverkite_estimator import SilverkiteEstimator
  from greykite.sklearn.transform.column_selector import ColumnSelector
label_desc: Use image node_id 1 for calling a global function with example usage: test_get_best_index() without return types