prompt: We are currently solving the following issue within our repository. Here is the issue text:
  --- BEGIN ISSUE ---
  Make test_tube optional
  **Is your feature request related to a problem? Please describe.**
  `test_tube` is only needed when using `TestTubeLogger`, thus it should not be an install requirement like `mlflow`.
  
  --- END ISSUE ---
  
  Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
  --- BEGIN FILES ---
  Path: `pytorch_lightning/logging/__init__.py`
  Content:
  ```
  1 from .base import LightningLoggerBase, rank_zero_only
  2 from .test_tube_logger import TestTubeLogger
  3 
  4 try:
  5     from .mlflow_logger import MLFlowLogger
  6 except ModuleNotFoundError:
  7     pass
  8
  ```
  --- END FILES ---
  
  Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.
  
  Here is an example:
  
  ```diff
  diff --git a/examples/server_async.py b/examples/server_async.py
  --- a/examples/server_async.py
  +++ b/examples/server_async.py
  @@ -313,4 +313,4 @@
   
   
   if __name__ == "__main__":
  -    asyncio.run(run_async_server("."), debug=True)
  +    asyncio.run(run_async_server(), debug=True)
  diff --git a/examples/server_sync.py b/examples/server_sync.py
  --- a/examples/server_sync.py
  +++ b/examples/server_sync.py
  @@ -313,5 +313,5 @@
   
   
   if __name__ == "__main__":
  -    server = run_sync_server(".")
  +    server = run_sync_server()
       server.shutdown()
  
  ```
  
golden_diff: diff --git a/pytorch_lightning/logging/__init__.py b/pytorch_lightning/logging/__init__.py
  --- a/pytorch_lightning/logging/__init__.py
  +++ b/pytorch_lightning/logging/__init__.py
  @@ -1,6 +1,9 @@
   from .base import LightningLoggerBase, rank_zero_only
  -from .test_tube_logger import TestTubeLogger
   
  +try:
  +    from .test_tube_logger import TestTubeLogger
  +except ModuleNotFoundError:
  +    pass
   try:
       from .mlflow_logger import MLFlowLogger
   except ModuleNotFoundError:
  
verification_info: {"golden_diff": "diff --git a/pytorch_lightning/logging/__init__.py b/pytorch_lightning/logging/__init__.py\n--- a/pytorch_lightning/logging/__init__.py\n+++ b/pytorch_lightning/logging/__init__.py\n@@ -1,6 +1,9 @@\n from .base import LightningLoggerBase, rank_zero_only\n-from .test_tube_logger import TestTubeLogger\n \n+try:\n+    from .test_tube_logger import TestTubeLogger\n+except ModuleNotFoundError:\n+    pass\n try:\n     from .mlflow_logger import MLFlowLogger\n except ModuleNotFoundError:\n", "issue": "Make test_tube optional\n**Is your feature request related to a problem? Please describe.**\r\n`test_tube` is only needed when using `TestTubeLogger`, thus it should not be an install requirement like `mlflow`.\n", "before_files": [{"content": "from .base import LightningLoggerBase, rank_zero_only\nfrom .test_tube_logger import TestTubeLogger\n\ntry:\n    from .mlflow_logger import MLFlowLogger\nexcept ModuleNotFoundError:\n    pass\n", "path": "pytorch_lightning/logging/__init__.py"}], "after_files": [{"content": "from .base import LightningLoggerBase, rank_zero_only\n\ntry:\n    from .test_tube_logger import TestTubeLogger\nexcept ModuleNotFoundError:\n    pass\ntry:\n    from .mlflow_logger import MLFlowLogger\nexcept ModuleNotFoundError:\n    pass\n", "path": "pytorch_lightning/logging/__init__.py"}]}