The Undocumented `is_chat_model` Function

because its usually set for you, or the docstring is usually enough. It probably should be mentioned somewhere. There's a lot of things to document, you could say the same for many things I'm sure

I've been meaning to make a more detailed page for OpenAILike for example

PRs welcome 🙂

Just for you: https://github.com/run-llama/llama_index/pull/17999

Honestly many fixes in there I had been meaning to make, including documenting is_chat_model 🙂