Allow in-place Chat history editing

[ncoghlan]

lmstudio-js supports in-place Chat history editing via:

• offering both mutable and immutable chat history and chat message instances via an internal mutability flag (using the MaybeMutable base class)
• the .replaceText() method on saved messages (there are also .appendFile() and appendText() methods on messages)
• the .replaceSystemPrompt() method to remove all previously added system prompt messages and insert the given prompt at the start of the chat history
• the .filterInPlace() method to process all currently saved messages with the given filtering callback
• the .pop() method
• supporting direct iteration over and indexed access to the messages saved in the chat history

The Python SDK should offer similar capabilities (although the exact spelling may differ).

[ncoghlan]

I was going to mark this as "Good first issue", since the TypeScript SDK offers a starting point for the Python SDK API design, but there are some open design questions that need to be answered before it would really qualify for that marker.

There's no specific ETA on resolving those questions (folks that genuinely need this capability aren't blocked by the absence of a supported API, they just need to tinker with the ._messages field directly, which they understandably would prefer not to be doing).

[NullMagic2]

The problem with modifying ._messages is that you need to know how the object is structured internally, and there's no guarantee the implementation will remain constant. If you want to allow _messages to be modified, at the very least the internal structure would have to be well-documented in the API / tutorial.

[yagil]

@NullMagic2 what about creating a an empty Chat object, iterating over the old one and appending / modifying as needed?

[NullMagic2]

@NullMagic2 what about creating a an empty Chat object, iterating over the old one and appending / modifying as needed?

For my own solution, I'm creating my own chat object and then converting to the proper format using Chat.from_history() but that's much slower and less than ideal when compared to simple in-place editing.

The reason I do that as opposed to just editing ._messages is because Chat.from_history() is a public documented API, and if I have my own structure, at least I know it'll behave a particular way.