code: def test_eval_hook(self):
      model = _SimpleModel()
      dataloader = self._data_loader("cpu")
      opt = torch.optim.SGD(model.parameters(), 0.1)
  
      for total_iter, period, eval_count in [
          (30, 15, 2),
          (31, 15, 3),
          (20, 0, 1),
      ]:
          test_func = mock.Mock(return_value={"metric": 3.0})
          trainer = SimpleTrainer(model, dataloader, opt)
          trainer.register_hooks([hooks.EvalHook(period, test_func)])
          trainer.train(0, total_iter)
          self.assertEqual(test_func.call_count, eval_count)
  
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 10 for calling the TestTrainer obj's underlying member method code with example usage: obj.test_eval_hook() without return types