Incorrect URI Prefix Stripping in MLflowLogger

[awindmann]

Bug description

Problem:
The save_dir property in the MLFlowLogger class currently uses str.lstrip() to remove the LOCAL_FILE_URI_PREFIX ("file:") from the tracking URI. This method can unintentionally strip additional characters that match those in the prefix. For example, "file:logs" would be incorrectly modified to "ogs" because lstrip() removes all individual characters that appear in the prefix string, not just the prefix itself.

Minimal Example:

from pytorch_lightning.loggers import MLFlowLogger

logger0 = MLFlowLogger(
    save_dir='logs'
)
logger1 = MLFlowLogger(
    save_dir='experiments'
)
logger2 = MLFlowLogger(
    save_dir='runs'  # this should work, as mlflow.LOCAL_FILE_URI_PREFIX ('file:') does not contain r
)
print(logger0.save_dir)  # ogs
print(logger1.save_dir)  # xperiments
print(logger2.save_dir)  # runs

Proposed Solutions:
For Python 3.9 and later: Utilize str.removeprefix(), which is designed to remove a specified prefix only if the string starts with it:

if self._tracking_uri.startswith(LOCAL_FILE_URI_PREFIX):
    return self._tracking_uri.removeprefix(LOCAL_FILE_URI_PREFIX)
return None

For Python 3.8 and earlier: Unfortunately, str.removeprefix() was introduced with Python 3.9.0, so another approach would have to be used. One possible solution would be to simply slice off the length of the prefix.

if self._tracking_uri.startswith(LOCAL_FILE_URI_PREFIX):
    return self._tracking_uri[len(LOCAL_FILE_URI_PREFIX):]
return None

What version are you seeing the problem on?

v2.4

How to reproduce the bug

No response

Error messages and logs

# Error messages and logs here please

Environment

Current environment

#- PyTorch Lightning Version (e.g., 2.4.0):
#- PyTorch Version (e.g., 2.4):
#- Python version (e.g., 3.12):
#- OS (e.g., Linux):
#- CUDA/cuDNN version:
#- GPU models and configuration:
#- How you installed Lightning(`conda`, `pip`, source):

More info

No response