[Python] Replace last two row values in a grouped polars DataFrame

I need to replace the last two values in the value column of a pl.DataFrame with zeros, whereby I need to group_by the symbol column.

import polars as pl

df = pl.DataFrame(
{"symbol": [*["A"] * 4, *["B"] * 4], "value": range(8)}
)

shape: (8, 2)
┌────────┬───────┐
│ symbol ┆ value │
│ --- ┆ --- │
│ str ┆ i64 │
╞════════╪═══════╡
│ A ┆ 0 │
│ A ┆ 1 │
│ A ┆ 2 │
│ A ┆ 3 │
│ B ┆ 4 │
│ B ┆ 5 │
│ B ┆ 6 │
│ B ┆ 7 │
└────────┴───────┘


Here is my expected outcome:

shape: (8, 2)
┌────────┬───────┐
│ symbol ┆ value │
│ --- ┆ --- │
│ str ┆ i64 │
╞════════╪═══════╡
│ A ┆ 0 │
│ A ┆ 1 │
│ A ┆ 0 │<-- replaced
│ A ┆ 0 │<-- replaced
│ B ┆ 4 │
│ B ┆ 5 │
│ B ┆ 0 │<-- replaced
│ B ┆ 0 │<-- replaced
└────────┴───────┘

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