deprecate using None for code_execution_config (microsoft#1506)

autogen/agentchat/conversable_agent.py

@@ -7,6 +7,7 @@
 import re
 from collections import defaultdict
 from typing import Any, Awaitable, Callable, Dict, List, Literal, Optional, Tuple, Type, TypeVar, Union
+import warnings
 
 from .. import OpenAIWrapper
 from ..cache.cache import Cache
@@ -69,7 +70,7 @@ def __init__(
         max_consecutive_auto_reply: Optional[int] = None,
         human_input_mode: Optional[str] = "TERMINATE",
         function_map: Optional[Dict[str, Callable]] = None,
-        code_execution_config: Optional[Union[Dict, Literal[False]]] = None,
+        code_execution_config: Union[Dict, Literal[False]] = {},
         llm_config: Optional[Union[Dict, Literal[False]]] = None,
         default_auto_reply: Optional[Union[str, Dict, None]] = "",
         description: Optional[str] = None,
@@ -139,6 +140,13 @@ def __init__(
         # Initialize standalone client cache object.
         self.client_cache = None
 
+        if code_execution_config is None:
+            warnings.warn(
+                "Using None to signal a default code_execution_config is deprecated. "
+                "Use {} to use default or False to disable code execution.",
+                stacklevel=2,
+            )
+
         self._code_execution_config: Union[Dict, Literal[False]] = (
             {} if code_execution_config is None else code_execution_config
         )