accelerate

9baf95be - Fix MLFLOW_NESTED_RUN never being able to turn nesting off (#4223)

Fix MLFLOW_NESTED_RUN never being able to turn nesting off (#4223) `MLflowTracker.__init__` does: nested_run = os.environ.get("MLFLOW_NESTED_RUN", nested_run) and passes the result straight to `mlflow.start_run(nested=...)`. When the variable is set the value is a string, and every non-empty string is truthy, so `MLFLOW_NESTED_RUN=False` turns nesting on. The docstring says the variable has priority over the argument, which means `nested_run=False` in code cannot win either. Setting the variable to any value at all enables nesting. `tags` two lines above already converts its string form, so the conversion is the only thing missing here. `str_to_bool` is what the rest of the library uses for boolean environment variables.