Function parallel_stats 

pub fn parallel_stats<T, I, F>(
    items: I,
    extract: F,
) -> (usize, f64, Option<f64>, Option<f64>)
where
    T: Send,
    I: ParallelIterator<Item = T>,
    F: Fn(&T) -> f64 + Sync + Send,

Compute multiple aggregations in a single parallel pass.

Returns (count, sum, min, max) for the extracted values.