Requirements: Don't force fastchat installation

Fastchat requires a lot of dependencies such as transformers, peft,
and accelerate which are heavy. This is not useful unless a user
wants to add a shim for the chat completion endpoint.

Instead, try importing fastchat and notify the console of the error.

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

OAI/utils.py

@@ -1,5 +1,4 @@
 import pathlib
-from fastchat.model.model_adapter import get_conversation_template, Conversation
 from OAI.types.completion import CompletionResponse, CompletionRespChoice
 from OAI.types.chat_completion import (
     ChatCompletionMessage,
@@ -10,8 +9,17 @@ from OAI.types.chat_completion import (
 )
 from OAI.types.common import UsageStats
 from OAI.types.model import ModelList, ModelCard
+from packaging import version
 from typing import Optional, List
 
+# Check fastchat
+try:
+    import fastchat
+    from fastchat.model.model_adapter import get_conversation_template
+    _fastchat_available = True
+except ImportError:
+    _fastchat_available = False
+
 def create_completion_response(text: str, model_name: Optional[str]):
     # TODO: Add method to get token amounts in model for UsageStats
 
@@ -78,6 +86,21 @@ def get_model_list(model_path: pathlib.Path):
     return model_card_list
 
 def get_chat_completion_prompt(model_path: str, messages: List[ChatCompletionMessage]):
+    # Check if fastchat is available
+
+    if not _fastchat_available:
+        raise ModuleNotFoundError(
+            "Fastchat must be installed to parse these chat completion messages.\n"
+            "Please run the following command: pip install fschat[model_worker]"
+        )
+    if version.parse(fastchat.__version__) < version.parse("0.2.23"):
+        raise ImportError(
+            "Parsing these chat completion messages requires fastchat 0.2.23 or greater. "
+            f"Current version: {fastchat.__version__}\n"
+            "Please upgrade fastchat by running the following command: "
+            "pip install -U fschat[model_worker]"
+        )
+
     conv = get_conversation_template(model_path)
     for message in messages:
         msg_role = message.role