Python: Fix function calling concept example.

[moonbox3]

Motivation and Context

A function calling plugin example is failing due to an incorrect chat completion base method. Additionally, if one specifies to enable function calling with auto invoke set to False, and they don't provide a kernel, then there is no error thrown.

Description

This PR:

• Fixes the concept example that shows three different ways to handle function calling.
• Fixes Python: The openai_function_calling_with_custom_plugin.py sample has several bugs #6453
• Adjusts the error checks for the kernel and arguments in the open_ai_chat_completion_base: manual function calling doesn't require arguments, so don't throw if they aren't provided; however, it does require a kernel, which is used to configure the tools for the settings, so this check has to be by itself.
• Add a unit test to exercise slightly different behavior.

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 3.10 Test Coverage Report •

File	Stmts	Miss	Cover	Missing
semantic_kernel/connectors/ai/open_ai/services
open_ai_chat_completion_base.py	219	96	56%	97, 101, 121, 146–150, 174, 178, 182, 198–203, 220–248, 251–262, 277–284, 295–303, 319–326, 347, 355, 361–364, 376–379, 410, 449, 454, 459–464, 468–475, 479–491, 513, 523–534
TOTAL	6098	786	87%

Python 3.10 Unit Test Overview

Tests	Skipped	Failures	Errors	Time
1403	1 💤	0 ❌	0 🔥	22.642s ⏱️

[eavanvalkenburg]

Would it be possible to start adding these sample to sample tests? In a similar approach as the learn resources ones, but perhaps with individual tests to account for more complex things!

[moonbox3]

Would it be possible to start adding these sample to sample tests? In a similar approach as the learn resources ones, but perhaps with individual tests to account for more complex things!

Yes, let's do it. I am going to start adding OpenAPI unit tests now, as we don't have any. I will start adding some of these concept examples as more tests.