handle diff chat templates

s2s_pipeline.py

@@ -470,7 +470,7 @@ class LanguageModelHandlerArguments:
         }
     )
     init_chat_role: str = field(
-        default="system",
+        default=None,
         metadata={
             "help": "Initial role for setting up the chat context. Default is 'system'."
         }
@@ -503,7 +503,7 @@ class LanguageModelHandler(BaseHandler):
             torch_dtype="float16",
             gen_kwargs={},
             user_role="user",
-            init_chat_role="system", 
+            init_chat_role=None, 
             init_chat_prompt="You are a helpful AI assistant.",
         ):
         self.tokenizer = AutoTokenizer.from_pretrained(model_name)
@@ -522,9 +522,13 @@ class LanguageModelHandler(BaseHandler):
             skip_prompt=True,
             skip_special_tokens=True,
         )
-        self.chat = [
-            {"role": init_chat_role, "content": init_chat_prompt}
-        ]
+        self.chat = []
+        if init_chat_role:
+            if not init_chat_prompt:
+                raise ValueError(f"An initial promt needs to be specified when setting init_chat_role.")
+            self.chat.append(
+                {"role": init_chat_role, "content": init_chat_prompt}
+            )
         self.gen_kwargs = {
             "streamer": self.streamer,
             "return_full_text": False,