Function substrate_fixed::transcendental::powi

pub fn powi<S, D>(operand: S, exponent: i32) -> Result<D, ()> where
    S: Fixed + PartialOrd<I9F23>,
    D: Fixed + PartialOrd<I9F23> + From<S> + From<I9F23>,
    D::Bits: Copy + ToFixed + AddAssign + BitOrAssign + ShlAssign, 

power with integer exponend