code: def test_scaling_config_pgf_equivalance(
      trainer_resources,
      resources_per_worker_and_use_gpu,
      num_workers,
      placement_strategy,
  ):
      resources_per_worker, use_gpu = resources_per_worker_and_use_gpu
      scaling_config = ScalingConfig(
          trainer_resources=trainer_resources,
          num_workers=num_workers,
          resources_per_worker=resources_per_worker,
          use_gpu=use_gpu,
          placement_strategy=placement_strategy,
      )
      try:
          pgf = scaling_config.as_placement_group_factory()
          scaling_config_from_pgf = (
              ScalingConfig.from_placement_group_factory(pgf)
          )
          assert scaling_config == scaling_config_from_pgf
          assert (
              scaling_config_from_pgf.as_placement_group_factory()
              == pgf
          )
      except ValueError as e:
          # We do not have to test invalid placement group factories
          assert str(e) == (
              "Cannot initialize a ResourceRequest with an empty head "
              "and zero worker bundles."
          )
  
imports: import pytest
  import ray
  from ray.train import Checkpoint, CheckpointConfig, ScalingConfig
  from ray.air._internal.config import ensure_only_allowed_dataclass_keys_updated
  from ray.data.preprocessor import Preprocessor
  from ray.train.trainer import BaseTrainer
label_desc: Use image node_id 8 for calling a global function with example usage: test_scaling_config_pgf_equivalance(trainer_resources, resources_per_worker_and_use_gpu, num_workers, placement_strategy) without return types