make work with langchain updates

app.py

@@ -1,13 +1,15 @@
 import os
-from pathlib import Path
 
 import gradio as gr
+from langchain.chains import RetrievalQA
+from langchain_core.vectorstores import VectorStoreRetriever
+from langchain_openai import OpenAI
+from openai import OpenAI as OpenAIClient
+
 import hpqa
-from langchain import VectorDBQA
-from langchain.llms import OpenAI
 
 os.environ["OPENAI_API_KEY"] = ""
-index_path = Path("data/hpqa_faiss_index_500")
+index_path = hpqa.LOCAL_DATA_PATH / "hpqa_faiss_index_500"
 
 
 examples = [
@@ -20,19 +22,24 @@ examples = [
 ]
 
 
-def api(question, temperature, api_key=None):
+def api(question, temperature, model, api_key=None):
     if api_key is None or len(api_key) == 0:
         return "You must provide an OpenAI API key to use this demo 👇"
     if len(question) == 0:
         return ""
     document_store = hpqa.load_document_store(index_path, openai_api_key=api_key)
-    chain = VectorDBQA.from_chain_type(
+
+    client = OpenAIClient(api_key=api_key)
+    models = [m.id for m in client.models.list().data if "gpt" in m.id if "vision" not in m.id]
+    if model not in models:
+        model_list = "\n".join(models)
+        return f"😬 {model} not a valid model name. Choose from:\n\n{model_list}"
+
+    chain = RetrievalQA.from_llm(
         llm=OpenAI(temperature=temperature, openai_api_key=api_key),
-        chain_type="stuff",
-        vectorstore=document_store,
-        return_source_documents=True,
+        retriever=VectorStoreRetriever(vectorstore=document_store),
     )
-    response = chain(question)
+    response = chain.invoke(question)
     return response["result"].strip()
 
 
@@ -49,8 +56,10 @@ with demo:
                 btn = gr.Button("Submit", variant="primary")
         with gr.Column():
             answer = gr.Textbox(lines=4, label="Answer")
-            openai_api_key = gr.Textbox(type="password", label="OpenAI API key")
-    btn.click(api, [question, temperature, openai_api_key], answer)
+            with gr.Row():
+                model = gr.Textbox(value="gpt-3.5-turbo-instruct", label="OpenAI Model")
+                openai_api_key = gr.Textbox(type="password", label="OpenAI API key")
+    btn.click(api, [question, temperature, model, openai_api_key], answer)
     clear.click(lambda _: "", question, question)
     gr.Examples(examples, question)
     gr.Markdown("💻 Checkout the `hpqa` source code on [GitHub](https://github.com/johnnygreco/hpqa).")