这段程序会输出什么？

import polars as pl

sales = pl.DataFrame(
    {
        "order_id": [1, 2, 3],
        "region": ["East", "West", "East"],
        "amount": [10, 20, 30],
    }
)
result = sales.with_columns(
    pl.col("amount").sum().over("region").alias("region_total")
).select("order_id", "region_total")

print(result.rows())