Function prod 

pub fn prod<T, D>(
    a: &Array<T, D>,
    axis: Option<usize>,
) -> Result<Array<T, IxDyn>, FerrayError>
where
    T: Element + Mul<Output = T> + Copy + Send + Sync,
    D: Dimension,

Product of array elements over a given axis.

Note: Unlike NumPy, which auto-promotes integer products, ferray returns the same type as the input. For large integer arrays this may overflow. Equivalent to numpy.prod.