Update app.py

app.py

@@ -3,7 +3,7 @@ import sqlite3
 import uuid
 import langchain
 from langchain_google_genai import GoogleGenerativeAI
-from langchain_core.prompts import ChatPromptTemplate,MessagePlaceholder
+from langchain_core.prompts import ChatPromptTemplate,MessagesPlaceholder
 from langchain_core.output_parser import StrOutputParser
 from langchain_community.chat_message_histories import SQLChatMessageHistory
 from langchain_core.runnables.history import RunnablesWithMessageHistory