Function rv::data::extract_stat_then

pub fn extract_stat_then<Fx, X, Ctor, Fnx, Y>(
    x: &DataOrSuffStat<'_, X, Fx>, 
    stat_ctor: Ctor, 
    f_stat: Fnx
) -> Y where
    Fx: HasSuffStat<X>,
    Fx::Stat: Clone,
    Ctor: Fn() -> Fx::Stat,
    Fnx: Fn(Fx::Stat) -> Y, 

Convert a DataOrSuffStat into a Stat then do something with it