Allow additional tools at runtime

[TomeHirata]

This PR allows tools to maintain states during the lifespan of each ReAct.forward without affecting other executions by allowing users to pass additional tools to forward. Users can create a tool class that mutates instance variables.

class Counter():
    def __init__(self):
        self.count = 0

    def __call__(self, i: int):
        self.count += i
        return self.count

counter = Counter()

react = dspy.ReAct("max -> sum:int", tools=[])
react(max=5, additional_tools=[Counter()])

[chenmoneygithub]

One minor comment

[TomeHirata]

This part feels a bit downgraded, but at the same time, I wouldn't dynamically update the signature at runtime.

[chenmoneygithub]

This feels a little scary because it's hard to tell if this is going to cause regression or not.

@okhat From your experience, do you think LM can remember only to choose from provided tool without the Literal constrant?

[TomeHirata]

Yeah, tool names are passed to the LLM in the same call, so LLMs should have enough context. We could dynamically construct the literal at runtime, but I think it would increase the complexity so want to avoid it unless it causes regression.

[chenmoneygithub]

A few minor comments, otherwise LGTM!

[chenmoneygithub]

This feels a little scary because it's hard to tell if this is going to cause regression or not.

@okhat From your experience, do you think LM can remember only to choose from provided tool without the Literal constrant?