Update app.py

app.py

@@ -8,7 +8,7 @@ from langchain.embeddings import HuggingFaceEmbeddings
 from langchain.vectorstores import FAISS
 from langchain.memory import ConversationBufferMemory
 from langchain.chains import ConversationalRetrievalChain
-from langchain.llms import HuggingFaceHub
+from langchain.llms import OpenAI
 
 # Load environment variables
 load_dotenv()
@@ -42,7 +42,7 @@ def get_vectorstore(text_chunks):
 
 def get_conversation_chain(vectorstore):
     try:
-        llm = HuggingFaceHub(repo_id="mistralai/Mistral-7B-Instruct-v0.1", model_kwargs={"temperature": 0.5})
+        llm = OpenAI(model_name="gpt-4", api_key=os.getenv("OPENAI_API_KEY"))
         memory = ConversationBufferMemory(memory_key='chat_history', return_messages=True)
         
         return ConversationalRetrievalChain.from_llm(