Update main.py

main.py

@@ -17,6 +17,7 @@ from langchain.schema.runnable import Runnable
 from langchain.schema.runnable.config import RunnableConfig
 from langchain.schema.runnable import Runnable, RunnablePassthrough, RunnableLambda
 from langchain.prompts import ChatPromptTemplate, MessagesPlaceholder
+from langchain_core.prompts import PromptTemplate
 
 @cl.password_auth_callback
 def auth_callback(username: str, password: str):