[Python] Select the first and last row per group in Polars dataframe

I'm trying to use polars dataframe where I would like to select the first and last row per group. Here is a simple example selecting the first row per group:

import polars as pl

df = pl.DataFrame(
{
"a": [1, 2, 2, 3, 4, 5],
"b": [0.5, 0.5, 4, 10, 14, 13],
"c": [True, True, True, False, False, True],
"d": ["Apple", "Apple", "Apple", "Banana", "Banana", "Banana"],
}
)
result = df.group_by("d", maintain_order=True).first()
print(result)


Output:

shape: (2, 4)
┌────────┬─────┬──────┬───────┐
│ d ┆ a ┆ b ┆ c │
│ --- ┆ --- ┆ --- ┆ --- │
│ str ┆ i64 ┆ f64 ┆ bool │
╞════════╪═════╪══════╪═══════╡
│ Apple ┆ 1 ┆ 0.5 ┆ true │
│ Banana ┆ 3 ┆ 10.0 ┆ false │
└────────┴─────┴──────┴───────┘


This works good and we can use .last to do it for the last row. But how can we combine these in one group_by?

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