Introduce chatModels

[ChristianSch]

I already started with openai but have the need to discuss how we want to map langchain to langchaingo in a few instances. I'll make a PR soon.

[ChristianSch]

I would like to highlight my biggest problem. We have the ChatMessage as follows:

type ChatMessage interface {
	GetText() string
	GetType() ChatMessageType // <- role
}

The openAI API needs separated role and message fields though: https://platform.openai.com/docs/api-reference/chat/create. They are required.

The LLM contract allows passing strings only though.

// LLM is a langchaingo Large Language Model.
type LLM interface {
	Call(prompt string, stopWords []string) (string, error)
	Generate(prompts []string, stopWords []string) ([]*Generation, error)
}

The reference implementation seems to handle it by not using string-only messages:

chat([HumanMessage(content="Translate this sentence from English to French. I love programming.")])

Maybe we could generalize the LLM input to be a BaseMessage as well, and then strongly type it for all implementations? (Normal LLMs just get a text as input, chat role and text etc.)

What are everyone's thoughts? (@tmc?)

[tmc]

Hmm. I think we need to think through if “type” is sufficiently distinct from “role”. We have the role field on the GenericChatMessage struct.

[ChristianSch]

What's the type based upon?

[tmc]

What's the type based upon?

That's just a copy of the concept from https://github.com/hwchase17/langchain/blob/master/langchain/schema.py#L88

See "role" here: https://github.com/hwchase17/langchain/blob/master/langchain/schema.py#L106 (and used here: https://github.com/hwchase17/langchain/blob/master/langchain/schema.py#L33)

@ChristianSch sorry I missed your follow-up comment here. Please feel free to join us in the langchain chat in the #langchain-go channel.

[ChristianSch]

Ahhh ok. So we'd need to have a look. It's not very self-explanatory haha.

No worries. Which platform @tmc? Discord, Gitter, Matrix?

[tmc]

Ahhh ok. So we'd need to have a look. It's not very self-explanatory haha.

No worries. Which platform @tmc? Discord, Gitter, Matrix?

Sorry I should have indicated, we're in the langchain discord. (we should put this in the README..).