Example doesn't work

This approach doesn't work unfortunately, you'll get

```
Failed to save: Unable to reserve cache with key KEY, another job may be creating this cache. More details: Cache already exists. Scope: refs/pull/PR/merge, Key: KEY, Version: 32469cd0a0171f4072572dbbdd99cf227a78adb8e7a91bdebb481b28c3b05083
Warning: Cache save failed.
```

Start by inspecting the repository's GitHub Actions cache restore, delete, and save example, then reproduce the reported cache reservation error. Determine why the example reaches “Cache already exists” and update the example so its documented approach works without the failed cache save warning.

索引モデルが issue の本文から書いたものです。