Function substrate_fixed::transcendental::ln

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

natural logarithm