code: def test_step(self, *args, **kwargs):
      return {
          str(i): trainer.test_step(*args, **kwargs)
          for i, trainer in enumerate(self._trainers)
      }
  
imports: import bisect
  import functools
  import itertools
  from collections import OrderedDict
  from typing import Dict, List, Tuple
  import torch.nn
  from pytorch_lightning.loops.optimization.optimizer_loop import ClosureResult
  from reagent.core.utils import lazy_property
  from .reagent_lightning_module import ReAgentLightningModule
label_desc: Use image node_id 16 for calling the MultiStageTrainer obj's underlying member method code with example usage: obj.test_step() and returns: unknown