General Enhancements in agentchat

[WaelKarkoub]

Why are these changes needed?

I noticed some inconsistencies in the formatting of the files, error handling, and type hints. I've only cleaned up the mistakes that I found were "obvious."

Related issue number

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://microsoft.github.io/autogen/docs/Contribute#documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 86.48649% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 47.02%. Comparing base (d711bd8) to head (0ecbd69).

Files	Patch %	Lines
autogen/agentchat/conversable_agent.py	60.00%	2 Missing and 2 partials ⚠️
autogen/agentchat/groupchat.py	88.88%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #1729       +/-   ##
===========================================
+ Coverage   36.10%   47.02%   +10.92%     
===========================================
  Files          63       63               
  Lines        6658     6681       +23     
  Branches     1470     1599      +129     
===========================================
+ Hits         2404     3142      +738     
+ Misses       4056     3284      -772     
- Partials      198      255       +57     

Flag	Coverage Δ
unittests	46.95% <86.48%> (+10.84%)	⬆️

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[ekzhu]

@sonichi @qingyun-wu this change requires open ai tests.

[sonichi]

@sonichi @qingyun-wu this change requires open ai tests.

Then it needs to be made from the main repo. @WaelKarkoub could you create a branch in the main repo and then make a PR?