code: def test_init_factory_function(self) -> None:
      generation_step = GenerationStep(model=get_sobol, num_trials=-1)
      self.assertEqual(
          generation_step.model_specs,
          [
              FactoryFunctionModelSpec(
                  factory_function=get_sobol,
                  model_kwargs=None,
                  model_gen_kwargs=None,
              )
          ],
      )
  
imports: import logging
  from logging import Logger
  from unittest.mock import patch, PropertyMock
  from ax.core.base_trial import TrialStatus
  from ax.core.observation import ObservationFeatures
  from ax.exceptions.core import UserInputError
  from ax.modelbridge.cross_validation import DiagnosticCriterion, MetricAggregation, SingleDiagnosticBestModelSelector
  from ax.modelbridge.factory import get_sobol
  from ax.modelbridge.generation_node import GenerationNode, GenerationStep
  from ax.modelbridge.model_spec import FactoryFunctionModelSpec, ModelSpec
  from ax.modelbridge.registry import Models
  from ax.modelbridge.transition_criterion import MaxTrials
  from ax.utils.common.logger import get_logger
  from ax.utils.common.testutils import TestCase
  from ax.utils.testing.core_stubs import get_branin_experiment
  from ax.utils.testing.mock import fast_botorch_optimize
label_desc: Use image node_id 4 for calling the TestGenerationStep obj's underlying member method code with example usage: obj.test_init_factory_function() without return types