Update app.py

app.py

@@ -29,6 +29,7 @@ app = FastAPI()
 
 @app.get("/")
 def read_root():
+    app.state.vector_index = None
     return {"message": "Connected"}
 
 @tool
@@ -42,7 +43,7 @@ def retrieve(query_text):
     Returns:
     - str: Retrieved text from the document.
     """
-    if vector_index is None:
+    if not hasattr(app.state, "vector_index") or app.state.vector_index is None:
         return "Vector index not found. Please upload a file first."
     else:
         retriever = app.state.vector_index.as_retriever(similarity_top_k=3)