Debug: Resolve the DALLE Agent's self.client error. (#1798)

* Change defualt model for `lmm`

* Try to use PIL image for LMM's _oai_messages

* Update test cases and llava

* Remove redundant files

* Update the imports for lmm tests

* Test case fix

* Docstring update

* LMM notebook lint

* Typo correction for img_utils and its test

* Fix self.client bug for Dalle Agent
The self.client member variable is reserved for OpenAI's LLM-compatible
client, which requires usage summary support.
So, we rename self.client to self._dalle_client to resolve this issue

Author: BeibinLi

.gitignore

@@ -178,3 +178,5 @@ test/agentchat/test_agent_scripts/*
 
 # test cache
 .cache_test
+
+notebook/result.png

notebook/agentchat_dalle_and_gpt4v.ipynb

@@ -2,9 +2,7 @@
 from unittest.mock import MagicMock, patch
 
 import pytest
-
 import autogen
-
 from conftest import MOCK_OPEN_AI_API_KEY
 
 try: