code: def test_easy_pareto_experiment() -> None:
      # Checking MOO in cross-validation.
      objective_functions: tp.List[tp.Any] = [
          ArtificialFunction(
              "sphere", block_dimension=2, translation_factor=0.0
          )
          for _ in range(3)
      ]
      xps = helpers.SpecialEvaluationExperiment.create_crossvalidation_experiments(
          objective_functions, pareto_size=16
      )
      print(xps[0])
      optimizer = ng.optimizers.OnePlusOne(
          parametrization=2, budget=100
      )
      optimizer.minimize(xps[0], verbosity=2)
      assert (
          xps[0].evaluation_function(optimizer.pareto_front()[0]) ** 2
          < 0.001
      )
  
imports: import pickle
  import numpy
  import pytest
  import nevergrad
  from nevergrad.common import testing
  from nevergrad.functions import ArtificialFunction
  import nevergrad.common.typing
  from .None import base
  from .None import helpers
label_desc: Use image node_id 12 for calling a global function with example usage: test_easy_pareto_experiment() without return types