Function columns_to_projection 

pub fn columns_to_projection<T>(
    columns: &[T],
    schema: &Schema<Field, BTreeMap<PlSmallStr, PlSmallStr>>,
) -> Result<Vec<usize>, PolarsError>
where
    T: AsRef<str>,

Available on crate feature polars-io and (crate features avro or ipc_streaming or ipc or parquet) only.