Add example of good doc sting to CONTRIBUTING.md

[gagb]

What feature would you like to be added?

Template and example for doc string that works well with the Sphinx theme.

Why is this needed?

To invite higher quality contributions.

[gagb]

Can we also have an etiquette whether system prompts and descriptions (usually long strings) should be set directly in the constructor. This can make the docs look busy as show below. Instead, we could use class variables. cc @afourney

[afourney]

I feel like in the cases I looked at the documentation engine expanded the constants.

I do not believe all of those long prompts are actually specified directly in the constructors?

[gagb]

I feel like in the cases I looked at the documentation engine expanded the constants.

I do not believe all of those long prompts are actually specified directly in the constructors?

The engine expands if the constant is used as the default. If None is used, it won't expand it.