TL;DR: your polars install is a mix of versions from a partial upgrade. Uninstall polars fully, delete leftovers, and install one clean version.

## The error
```text
ImportError: cannot import name 'POLARS_STORAGE_CONFIG_KEYS' from 'polars.io.cloud._utils'
```

## Fix it
1. Uninstall polars:
   ```
   pip uninstall -y polars
   ```
   Expected: reports removal.
2. Check site-packages for a leftover polars folder and delete it by hand.
3. Install fresh:
   ```
   pip install polars
   ```
   Expected: install completes.
4. Verify:
   ```
   python -c "import polars; print(polars.__version__)"
   ```
   Expected: prints the version, no error.

## When this applies
Use this when `import polars` itself raises the POLARS_STORAGE_CONFIG_KEYS error, which signals mixed install files.

## When it does not apply
If your own code imports from polars.io.cloud._utils, stop; it is a private module. If the error is a different missing name, check the polars version first.

## Compatibility
Any polars version; this is an install-hygiene issue.

## Root cause
polars.io.cloud._utils is a private module whose contents change between releases. A partial upgrade (or pip plus conda both installing polars) leaves old and new files side by side, and the mismatched modules cannot import each other's names.

## Edge cases
polars ships a compiled binary per version; mixing the python files of one version with the binary of another produces exactly this class of error. In docker, pin the polars version so rebuilds stay consistent.