code: def test_default_trainer(self):
      # TODO: this test requires manifold access, so changed device to CPU. see: T88318502
      cfg = get_cfg()
      cfg.MODEL.DEVICE = "cpu"
      cfg.MODEL.META_ARCHITECTURE = "_SimpleModel"
      cfg.DATASETS.TRAIN = ("coco_2017_val_100",)
      with tempfile.TemporaryDirectory(prefix="detectron2_test") as d:
          cfg.OUTPUT_DIR = d
          trainer = DefaultTrainer(cfg)
  
          # test property
          self.assertIs(trainer.model, trainer._trainer.model)
          trainer.model = _SimpleModel()
          self.assertIs(trainer.model, trainer._trainer.model)
  
imports: import json
  import math
  import os
  import tempfile
  import time
  import unittest
  from unittest import mock
  import torch
  from fvcore.common.checkpoint import Checkpointer
  from torch import nn
  from detectron2 import model_zoo
  from detectron2.config import configurable, get_cfg
  from detectron2.engine import DefaultTrainer, SimpleTrainer, default_setup, hooks
  from detectron2.modeling.meta_arch import META_ARCH_REGISTRY
  from detectron2.utils.events import CommonMetricPrinter, JSONWriter
label_desc: Use image node_id 8 for calling the TestTrainer obj's underlying member method code with example usage: obj.test_default_trainer() without return types