Function _agg_helper_slice_no_null 

pub fn _agg_helper_slice_no_null<T, F>(groups: &[[IdxSize; 2]], f: F) -> Series
where
    F: Fn([IdxSize; 2]) -> T::Native + Send + Sync,
    T: PolarsNumericType,

Available on crate feature algorithm_group_by only.