simplify history handling in `ChatModel.create_completion`

evoprompt/models.py

@@ -281,11 +281,8 @@ class ChatModel:
 
         # a history is prepended to the messages, and we assume that it also includes a system message, i.e., we never add a system message in this case
         # TODO is it better to check for a system message in the history?
-        if history is not None:
-            messages = history + messages
-            [messages.insert(index, entry) for index, entry in enumerate(history)]
-        elif system_message:
-            messages = [self._get_system_message(system_message)] + messages
+        if history is None and system_message:
+            history = [self._get_system_message(system_message)]
 
         reponse, usage = self._create_completion(
             messages=messages,
@@ -296,7 +293,7 @@ class ChatModel:
         )
 
         messages.append(self._get_assistant_message(reponse))
-        return reponse, messages, usage
+        return reponse, history + messages, usage
 
 
 class LlamaChat(Llama, ChatModel):