Local?

Hey good work.

I need this to run locally. It looks like it's using the hugging face api.

```
HF_TOKEN = os.environ.get("HF_TOKEN")

prompt_node = PromptNode(
model_name_or_path="mistralai/Mistral-7B-Instruct-v0.1", api_key=HF_TOKEN, default_prompt_template=prompt_template
)
```

Will try to get it running locally but I think there is a haystack class needed for this.