Update backend.py

backend.py

@@ -217,14 +217,12 @@ def initialize_qa_system(_vector_store):
             api_key=os.environ.get("OPENAI_API_KEY"),
         )
 
-        # Define the prompt template
-        prompt = ChatPromptTemplate.from_messages(
-            [
-                ("system", "You are a helpful assistant"),
-                MessagesPlaceholder(variable_name="chat_history"),
-                ("human", "{input}"),
-            ]
-        )
+       prompt = ChatPromptTemplate.from_messages([
+            ("system", "You are a helpful assistant"),
+            MessagesPlaceholder(variable_name="chat_history"),   
+
+            ("human", "{input}"),
+            MessagesPlaceholder(variable_name="agent_scratchpad"),  
 
         # Define the tools
         tools = [