Add environment widget example

[MarcSkovMadsen]

Builds on #3 and #26. Review those ones first!

The EnvironmentWidgetBase class enables you to manage variable values from a combination of

• custom variable values
• environment variables
• user input.

(listed by order of precedence)

For example you might not have the resources to provide an OPENAI_API_KEY, WEAVIATE_API_KEY or LANGCHAIN_API_KEY. In that case you would would like to ask the user for it.

Inherit from this widget to create your own custom EnvironmentWidget.

This widget can make it easy to run the app in different environments

• locally: all keys might be set in os.environ
• hugging face: some keys might not be set in os.environ due to costs, but users can manually provide them.

After setting the WEAVIATE_API_KEY it looks like

See https://github.com/holoviz/panel/issues/5562 for more detail. Long term I think it could be useful if something like this was included in the Panel chat components.

[ahuang11]

I wasn't aware that there's a langchain API key.

[MarcSkovMadsen]

Me neither. I just saw it in an example

[ahuang11]

I don't think there's an api key for langchain. Couldn't find any docs for it; it's for OpenAI if that's what you meant. https://python.langchain.com/docs/get_started/quickstart#environment-setup

[MarcSkovMadsen]

At least Langchain puts an API key in their own docs. This is where I saw it. The key is probably for LangSmith. Have not tried it yet.

https://github.com/langchain-ai/chat-langchain

[MarcSkovMadsen]

I've merged with the current main branch. And everything should be ready to merge.

If you want, I can change the example to use another variable than the LANGCHAIN_API_KEY. Let me know.

If anything else is needed let me know.

[codecov-commenter]

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[ahuang11]

Thanks for contributing this! I'd love to migrate this into Panel too if Philipp agrees!