code: def test_tensorboard_log_sub_dir(tmp_path):
      class TestLogger(TensorBoardLogger):
          # for reproducibility
          @property
          def version(self):
              return "version"
  
          @property
          def name(self):
              return "name"
  
      trainer_args = {"default_root_dir": tmp_path, "max_steps": 1}
  
      # no sub_dir specified
      save_dir = tmp_path / "logs"
      logger = TestLogger(save_dir)
      trainer = Trainer(**trainer_args, logger=logger)
      assert trainer.logger.log_dir == os.path.join(
          save_dir, "name", "version"
      )
  
      # sub_dir specified
      logger = TestLogger(save_dir, sub_dir="sub_dir")
      trainer = Trainer(**trainer_args, logger=logger)
      assert trainer.logger.log_dir == os.path.join(
          save_dir, "name", "version", "sub_dir"
      )
  
      # test home dir (`~`) handling
      save_dir = "~/tmp"
      explicit_save_dir = os.path.expanduser(save_dir)
      logger = TestLogger(save_dir, sub_dir="sub_dir")
      trainer = Trainer(**trainer_args, logger=logger)
      assert trainer.logger.log_dir == os.path.join(
          explicit_save_dir, "name", "version", "sub_dir"
      )
  
      # test env var (`$`) handling
      test_env_dir = "some_directory"
      os.environ["TEST_ENV_DIR"] = test_env_dir
      save_dir = "$TEST_ENV_DIR/tmp"
      explicit_save_dir = f"{test_env_dir}/tmp"
      logger = TestLogger(save_dir, sub_dir="sub_dir")
      trainer = Trainer(**trainer_args, logger=logger)
      assert trainer.logger.log_dir == os.path.join(
          explicit_save_dir, "name", "version", "sub_dir"
      )
  
imports: import logging
  import os
  from argparse import Namespace
  from unittest import mock
  from unittest.mock import Mock
  import numpy
  import pytest
  import torch
  import yaml
  from lightning.pytorch import Trainer
  from lightning.pytorch.demos.boring_classes import BoringModel
  from lightning.pytorch.loggers import TensorBoardLogger
  from lightning.pytorch.loggers.tensorboard import _TENSORBOARD_AVAILABLE
  from lightning.pytorch.utilities.imports import _OMEGACONF_AVAILABLE
  from tests_pytorch.helpers.runif import RunIf
label_desc: Use image node_id 6 for calling a global function with example usage: test_tensorboard_log_sub_dir(tmp_path) and returns: str, str