Add token usage to messages

[ekzhu]

Resolves #4017

[victordibia]

Looks good, thanks!!

[auphof]

@ekzhu with the introduction of

autogen/python/packages/autogen-agentchat/src/autogen_agentchat/messages.py

Line 14 in 542dd28

model_usage: RequestUsage | None = None

I am experiencing a flurry of pydantic UserWarnings like Field "model_usage" in BaseMessage has conflict with protected namespace "model_".

This happens when i attempt something like from autogen_agentchat.logging import ConsoleLogHandler

I have managed to suppress it with doing the following model_config in BaseMessage

from pydantic import BaseModel, ConfigDict

class BaseMessage(BaseModel):
    """A base message."""

    # Work around to suppress protected namespace  checks, 
    # Without out this we get`UserWarnings`` like `Field "model_usage" in BaseMessage has conflict with protected namespace "model_".` `
    model_config = ConfigDict(protected_namespaces=())

    source: str
    """The name of the agent that sent this message."""

    model_usage: RequestUsage | None = None
    """The model client usage incurred when producing this message."""

However as per https://docs.pydantic.dev/2.1/usage/model_config/#protected-namespaces
By setting protected_namespaces=(), you're essentially disabling the protection for all namespaces, which allows you to use field names that would otherwise conflict with Pydantic's protected namespaces.

So, it's important to note a few things:

• This approach removes all namespace protections, which might lead to unexpected behavior if you're not careful with your field names.
• If possible, consider renaming the field to avoid the conflict altogether. For example, you could use usage_data instead of model_usage.

[ekzhu]

@auphof thanks for the catch, we will rename the field.