* Change "content" type in Conversable Agent
* content and system_message support str and List
Update for all other agents
* Content_str now also takes None as input
* Group Chat now works with LMM too
* Style: newline for import in Conversable Agentt
* Add test for gourpchat + lmm
* Resolve comments
1. Undo AssistantAgent changes
2. Modify the asserts and raises in `content_str` function and update
test accordingly.
* Undo AssistantAgent
* Update comments and add assertion for LMM
* Typo fix in docstring for content_str
* Remove “None” out conversable_agent.py
* Lint message to dict in multimodal_conversable_agent.py
* Address lint issues
* linting
* Move lmm test into contrib test
* Resolve 2 comments
* Move img_utils into contrib folder
* Resolve img_utils path issues