Update app.py

app.py

@@ -7,7 +7,7 @@ from langchain_openai import OpenAIEmbeddings
 from langchain_community.vectorstores import Chroma
 from langchain_core.messages import HumanMessage, AIMessage, ToolMessage
 from langchain.text_splitter import RecursiveCharacterTextSplitter
-from langgraph.graph import END, StateGraph, START
+from langgraph.graph import END, StateGraph  # Removed START import
 from langgraph.prebuilt import ToolNode
 from langgraph.graph.message import add_messages
 from typing_extensions import TypedDict, Annotated
@@ -18,6 +18,9 @@ import streamlit as st
 import requests
 from langchain.tools.retriever import create_retriever_tool
 
+# Define our own START constant
+START = "START"
+
 # ------------------------------
 # Dummy Data: Research & Development Texts
 # ------------------------------
@@ -45,8 +48,7 @@ development_docs = splitter.create_documents(development_texts)
 # ------------------------------
 embeddings = OpenAIEmbeddings(
     model="text-embedding-3-large",
-    # You can uncomment and set dimensions if needed:
-    # dimensions=1024
+    # dimensions=1024  # Uncomment if needed
 )
 research_vectorstore = Chroma.from_documents(
     documents=research_docs,