Python: Fixed Azure chat client for asynchronous filtering

[dmytrostruk]

Motivation and Context

Resolves: #1563

When Azure's asynchronous content filtering is enabled, streaming responses can contain annotation chunks where delta is None. Added a None check to handle these annotation messages gracefully.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? If yes, add "[BREAKING]" prefix to the title of the PR.

[markwallace-microsoft]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
packages/core/agent_framework/azure
_chat_client.py	79	4	94%	282, 284, 297–298
TOTAL	17431	2669	84%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
3149	213 💤	0 ❌	0 🔥	1m 3s ⏱️

[Copilot]

Pull request overview

This PR fixes a bug in the Azure OpenAI chat client where streaming responses with asynchronous content filtering enabled would fail due to None delta values. The fix adds a None check in the _parse_text_from_openai method override and includes a comprehensive test to verify the behavior.

Changes:

• Added None check in AzureOpenAIChatClient._parse_text_from_openai to handle empty deltas from async content filtering
• Added unit test to verify streaming handles None delta chunks correctly

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
python/packages/core/agent_framework/azure/_chat_client.py	Added None check before accessing delta properties to prevent AttributeError when Azure async content filtering returns None deltas
python/packages/core/tests/azure/test_azure_chat_client.py	Added test case that simulates streaming with None delta chunks followed by actual content