Function picks 

pub fn picks<T, R>(data: &[T], shape: [usize; 3], of: Picks) -> Vec<usize>
where
    T: Copy + PartialEq + Send + Sync,
    R: Reduction<T, Total = T>,

The row of the first item that gives each fold by R along the middle axis of data, an array of shape [outer, len, inner], for a reduction that picks one of its items, as Max and Min do. of chooses the folds, and the result lays out as their results do. Each row counts from the start of its lane. A fold whose items all leave it at R::unit(), as NaN items do for a float maximum, gives its first row.