pub fn map_column<'a, ColumnType: 'static, A: 'static, B: 'static>(
    column_data: &'a ColumnInformation<ColumnType>,
    column_idx: usize,
    indexes: &[usize],
    map_fn: A,
) -> Box<dyn Iterator<Item = B> + 'a>
where
    A: Fn(ColumnType) -> B,
    ColumnType: std::clone::Clone,
{
    let column_indexes: Vec<usize> = indexes
        .iter()
        .map(|idx| (column_data.columns * *idx) + column_idx)
        .collect::<Vec<usize>>();

    Box::new(
        column_indexes
            .into_iter()
            .map(move |index| map_fn(column_data.predictors[index].clone())),
    )
}