docstr: Test to ensure that we save the model correctly when save best model is set to True.
code: def test_ema_run_with_save_best_model(self, tmpdir):
      """Test to ensure that we save the model correctly when save best model is set to True."""
      tmp_path = tmpdir / "exp_manager_test"
      model = ExampleModel()
  
      trainer = Trainer(
          max_epochs=1,
          enable_checkpointing=False,
          logger=False,
          devices=1,
          limit_train_batches=1,
      )
      exp_manager(
          trainer,
          {
              "ema": {"enable": True},
              "explicit_log_dir": str(tmp_path),
              "checkpoint_callback_params": {"save_best_model": True},
          },
      )
      trainer.fit(model)
  
imports: import os.path
  from typing import Any, Dict, Union
  import pytest
  import pytorch_lightning
  import torch
  from omegaconf import DictConfig, OmegaConf
  from pytorch_lightning import Callback, Trainer
  from pytorch_lightning.utilities.exceptions import MisconfigurationException
  from pytorch_lightning.utilities.types import STEP_OUTPUT
  from nemo.collections.common.callbacks import EMA
  from nemo.collections.common.callbacks.ema import EMAOptimizer
  from nemo.core import ModelPT
  from nemo.utils.exp_manager import exp_manager
label_desc: Use image node_id 4 for calling the TestEMATrain obj's underlying member method code with example usage: obj.test_ema_run_with_save_best_model(tmpdir) without return types