Flet for Python doesn't work

Code Help Python
1

I installed Flеt via Packages.
I can’t run this code.

import flet as ft

def main(page: ft.Page):
    t = ft.Text(value="Hello, world!", color="green")
    page.controls.append(t)
    page.update()

ft.app(target=main)

append(t) underlined in red. When launched, a non-existent page opens in the browser in the next tab.