[Python] Lookup column name in column

Say I have

df = pl.DataFrame({
'a': [1, 2, 1],
'b': [2, 1, 2],
'c': [3, 3, 2],
'column': ['a', 'c', 'b'],
})


shape: (3, 4)
┌─────┬─────┬─────┬────────┐
│ a ┆ b ┆ c ┆ column │
│ --- ┆ --- ┆ --- ┆ --- │
│ i64 ┆ i64 ┆ i64 ┆ str │
╞═════╪═════╪═════╪════════╡
│ 1 ┆ 2 ┆ 3 ┆ a │
│ 2 ┆ 1 ┆ 3 ┆ c │
│ 1 ┆ 2 ┆ 2 ┆ b │
└─────┴─────┴─────┴────────┘


I want add a column which, for each row, take the value in the row corresponding to the column in column.

Expected output:

shape: (3, 5)
┌─────┬─────┬─────┬────────┬────────┐
│ a ┆ b ┆ c ┆ column ┆ lookup │
│ --- ┆ --- ┆ --- ┆ --- ┆ --- │
│ i64 ┆ i64 ┆ i64 ┆ str ┆ i64 │
╞═════╪═════╪═════╪════════╪════════╡
│ 1 ┆ 2 ┆ 3 ┆ a ┆ 1 │
│ 2 ┆ 1 ┆ 3 ┆ c ┆ 3 │
│ 1 ┆ 2 ┆ 2 ┆ b ┆ 2 │
└─────┴─────┴─────┴────────┴────────┘

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