Update app.py

app.py

@@ -132,7 +132,7 @@ class Chatbot:
         qa = ConversationalRetrievalChain.from_llm(
             llm=OpenAI(temperature=0.5),
             retriever=retriever,
-            memory=ConversationBufferMemory(return_messages=True),
+            memory=ConversationBufferMemory(memory_key="chat_history",return_messages=True),
             return_source_documents=False)
         # Set the question for which we want to find the answer
         res = []