feat: Update streaming chunk

[sjrl]

Related Issues

• fixes Extend StreamingChunk to have tool_call, tool_result, start and index #9358

Proposed Changes:

Updated StreamingChunk to add the fields tool_call, tool_call_result, index, and start to make it easier to format the stream in a streaming callback.

• Added new dataclass ToolCallDelta for the StreamingChunk.tool_call field to reflect that the arguments can be a string delta.
• Updated print_streaming_chunk and _convert_streaming_chunks_to_chat_message utility methods to use these new fields. This especially improves the formatting when using print_streaming_chunk with Agent.
• Updated OpenAIGenerator, OpenAIChatGenerator, HuggingFaceAPIGenerator, HuggingFaceAPIChatGenerator, HuggingFaceLocalGenerator and HuggingFaceLocalChatGenerator to follow the new dataclasses.
• Updated ToolInvoker to follow the StreamingChunk dataclass.

How did you test it?

• Added unit tests
• Tested Agent streaming locally with OpenAIChatGenerator

Before Changes

After Changes

• Notable differences
  • Possible to add the [ASSISTANT] header
  • Easier to have better spacing between sections (e.g. between two tool calls)

Notes for the reviewer

Just as a heads up ~450 lines of code change from the tests so don't bee too alarmed by the large PR.

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test: and added ! in case the PR includes breaking changes.
• I documented my code
• I ran pre-commit hooks and fixed any issue

[sjrl]

I thought about making

content = Union[str, ToolCallDelta, ToolCallResult]

but this would be a breaking change b/c users expect content to always be a string. And this breaks StreamingChunk to ChatMessage implementations (mostly in private methods).

[coveralls]

Pull Request Test Coverage Report for Build 15485894448

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

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Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall first build on update-streaming-chunk at 90.418%

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Totals
Change from base Build 15414807243:	90.4%
Covered Lines:	11512
Relevant Lines:	12732

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💛 - Coveralls

[tstadel]

Looks very good to me already. 👍

[sjrl]

In ToolInvoker the whole ToolCallResult is always sent so start is always True and index is just the current message index.

[sjrl]

Failing tests are fixed with this PR #9457

[julian-risch]

Looks quite good to me already! 👍 I have only minor comments and regarding Optional[bool] for start in StreamingChunk, I would like to better understand what the meaning of None would be.

[julian-risch]

Thanks for addressing the change requests! Another two small change requests and then the PR is ready to be merged!

[julian-risch]

LGTM! 👍