<V> Result<V,ERROR>
fmap(Fn1<VALUE,Result<V,ERROR>> mapper)
map(Fn1<VALUE,V> mapper)
default <RES> RES
map(Fn1<A,RES> f)
<E> Result<VALUE,E>
mapErr(Fn1<ERROR,E> mapper)
VALUE
unwrap(Fn1<ERROR,VALUE> errUnwrap)