update prepare_messages to work with multi turn

README.md

@@ -66,10 +66,16 @@ def prepare_messages(query: str, tools: Optional[dict[str, any]] = None) -> list
     if tools is None:
         tools = []
 
-    return [
-        {"role": "system", "content": SYSTEM_PROMPT},
-        {"role": "user", "content": prompt.render(tools=json.dumps(tools), query=query)}
-    ]
+    if conversation_history:
+        messages = conversation_history.copy()
+        messages.append({"role": "user", "content": query})
+    else:
+        messages = [
+            {"role": "system", "content": system_prompt},
+            {"role": "user", "content": prompt.render(tools=json.dumps(tools), query=query)}
+        ]
+
+    return messages
     
 ````