Function apply_binary

pub fn apply_binary<F>(a: Expr, b: Expr, f: F, output_type: GetOutput) -> Expr
where
    F: 'static + Fn(Column, Column) -> PolarsResult<Option<Column>> + Send + Sync,

Like map_binary, but used in a group_by-aggregation context.

See Expr::apply for the difference between map and apply.