Update app.py

app.py

@@ -79,7 +79,7 @@ def handle_query(user_message, temperature, chat_history):
         previous_answers = transform_history_for_langchain(chat_history)
 
         pdf_qa = ConversationalRetrievalChain.from_llm(
-            ChatOpenAI(temperature=temperature, model_name='gpt-4o'),
+            ChatOpenAI(temperature=temperature, model_name='gpt-4'),
             retriever=vectordb.as_retriever(search_kwargs={'k': 6}),
             return_source_documents=True,
             verbose=False