[Python] How to group dataframe rows into list in polars group_by

import polars as pl

df = pl.DataFrame(
{
'Letter': ['A', 'A', 'B', 'B', 'B', 'C', 'C', 'D','D','E'],
'Value': [1, 2, 3, 4, 5, 6, 7, 8, 9,10]
}
)


I want to group Letter and collect their corresponding Value in a List.

Related Pandas question: How to group dataframe rows into list in pandas groupby

I know pandas code will not work here:

df.group_by('a')['b'].apply(list)

TypeError: 'GroupBy' object is not subscriptable


Output will be:

| A ┆ [1, 2] │
│ B ┆ [3, 4, 5] │
│ C ┆ [6, 7] │
│ D ┆ [8, 9] │
│ E ┆ [10] |

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