Update app.py

app.py

@@ -2,7 +2,7 @@ from fastapi import FastAPI
 import gradio as gr
 app = FastAPI()
 @app.get("/")
-def read_main():
-    return {"message": "This is your main app"}
-io = gr.ChatInterface(respond_to_chat)
+def echo(message, history):
+    return message
+io = gr.ChatInterface(echo)
 app = gr.mount_gradio_app(app, io, path="/gradio")