Blank screen problem in spaces

I have copied below code form hugging face documentation when i try to run on locally it’s working fine and showing interface but when i try to run same code in hugging face spaces after building it’s showing running but i can’t see interface. it’s just showing blank white screen.

import gradio as gr

def greet(name):
return "Hello " + name + “!”

demo = gr.Interface(fn=greet, inputs=“text”, outputs=“text”)

demo.launch()