Read the code carefully

import asyncio
import contextvars

req_id = contextvars.ContextVar("req_id", default="none")


async def child():
    return f"child:{req_id.get()}"


async def isolated():
    req_id.set("req-B")
    return f"isolated:{req_id.get()}"


async def main():
    req_id.set("req-A")
    a = await child()
    t = asyncio.create_task(isolated())
    b = await t
    return [a, b, f"main:{req_id.get()}"]


print(asyncio.run(main()))

What will the program print? Write here: