ModuleNotFoundError: No module named 'langchain.retrievers'

I just tried to use RAGatouille but as soon as I `import ragatouille` I receive the following error:

```bash
ModuleNotFoundError: No module named 'langchain.retrievers'
```

The issue is that in the latest LangChain versions the `langchain.retrievers` module does not exist.
RAGatouille does not clearly specify which is the langchain version to use.
I'm using uv to manage my project and the latest langchain version is downloaded.

You should upgrade your imports.

Can you fix, please?

Start by reproducing the `import ragatouille` failure with the latest LangChain version and inspect the package imports reached by that entry point. Done means the import works with the supported LangChain version, and the required version or compatibility guidance is clearly specified.

Written by the indexing model from the issue text.