OAI: Add separator style fallback

Some models may return None for separator style with FastChat. Fall
back to LLAMA2 if this is the case.

Signed-off-by: kingbri <bdashore3@proton.me>

OAI/utils.py

@@ -16,6 +16,7 @@ from typing import Optional, List
 try:
     import fastchat
     from fastchat.model.model_adapter import get_conversation_template
+    from fastchat.conversation import SeparatorStyle
     _fastchat_available = True
 except ImportError:
     _fastchat_available = False
@@ -116,6 +117,9 @@ def get_chat_completion_prompt(model_path: str, messages: List[ChatCompletionMes
         )
 
     conv = get_conversation_template(model_path)
+    if conv.sep_style is None:
+        conv.sep_style = SeparatorStyle.LLAMA2
+
     for message in messages:
         msg_role = message.role
         if msg_role == "system":