Python: Update sort step method for assistant invoke.

[moonbox3]

Motivation and Context

At times, when the (Azure) OpenAI Assistant Agent makes a tool call, that tool call's creation timestamp is coming after the message creation timestamp (the message creation being the text that the assistant responds with). Currently in our code, if we have a tool call (FunctionCallContent), we first yield that, and then we make a call to get completed steps, to then yield more content like FunctionResultContent and TextContent. There will be two steps (or more, depending upon the number of tool calls).

Right now we sort the completed steps in this way:

completed_steps_to_process: list[RunStep] = sorted(
    [s for s in steps if s.completed_at is not None and s.id not in processed_step_ids],
    key=lambda s: s.created_at,
)

When there are no failures, it's because the tool call was created before the final message content (as has been since this assistant was first coded). However, it appears that processing on the server-side can cause fluctuations in when the steps are created/processed. When we have a failure, we now have the message_creation (TextContent) yielded before the FunctionResultContent, which if sent to an (Azure) OpenAI Chat Completion endpoint will break with a 400 because of the gap in the ordering between the FunctionCallContent and the FunctionResultContent:

FunctionCallContent
TextContent # this should follow `FunctionResultContent` (and it does during times when we don't see a 400)
FunctionResultContent

The 400 error isn't 100% repeatable because of server-side processing, so we will get the correct ordering:

FunctionCallContent
FunctionResultContent
TextContent

This PR updates the ordering of how we sort of the completed steps -- if we have a step_type == "tool_calls" and "message_creation", we sort to allow for "tool_calls" to come first, and any ties are broken by the step.completed_at timestamp. With this update, we no longer receive 400s because the ordering of the content types is correct when sending to an OpenAI model.

Description

This PR:

• Updates the way we sort completed messages during an assistant invoke.
• Adds logging for the assistant invoke method at the info level.
• Closes Python: Bug: Kernel Function plugin not working with AzureAssistantAgent #10141

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄

[markwallace-microsoft]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
semantic_kernel/agents/open_ai
open_ai_assistant_base.py	480	8	98%	255, 341–342, 752, 916, 919, 993, 1057
TOTAL	16709	1778	89%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
3001	4 💤	0 ❌	0 🔥	1m 20s ⏱️

[eavanvalkenburg]

should we add some unit tests for this mechanism?

[moonbox3]

should we add some unit tests for this mechanism?

We have unit tests covering - but I will add some to check the order of messages.