Support for generate and return tool_calls with Anthropic models

[bigbernnn]

The proposed changes include: 1/ Ability to use tools with .generate() 2/ Returning stop_reason and tool_calls to AIMessage when using tools in the response metadata

Support for function call using the generate function not directly implemented in ChatBedrock.

from bedrock import ChatBedrock

chat = ChatBedrock(
    model_id=model_id,
    model_kwargs={"temperature": 0.1},
)

class GetWeather(BaseModel):
    """Get the current weather in a given location"""

    location: str = Field(..., description="The city and state, e.g. San Francisco, CA")

llm_with_tools = chat.bind_tools([GetWeather])
llm_with_tools

messages = [
    HumanMessage(
        content="what is the weather like in San Francisco"
    )
]
ai_msg = llm_with_tools.generate(messages)
ai_msg

[Benjaminrivard]

Hi, Is there anything we can do to allow the PR to get merged ?

[marcoBongio]

Hi, is the _toolchoice argument of _bindtools method functioning? Because I would like to force the LLM to use a tool, but it does not seem to work. Are there any workarounds to do so? Thank you in advance.

[ssg-kstewart]

For those coming across this PR in search of a solution, I had an issue where the tools were not actually being called. I have created a PR against the fork created by @bigbernnn which can be found here. This has resolved my related issue here.

[devesh2003]

Can this please be reviewed and merged? Can't switch my existing codebase to bedrock due to this error.

# llm = ChatOpenAI(model="gpt-4o", openai_api_key=OPENAI_API_KEY) [WORKS FINE]
# llm = ChatAnthropic(model="claude-3-opus-20240229") [WORKS FINE]
llm = ChatBedrock(
    model_id="anthropic.claude-3-sonnet-20240229-v1:0",
    model_kwargs=dict(temperature=0),
) [ERROR]

ValueError: System message must be a string, instead was: <class 'list'>