mapJust<K> method
A method to chain access to data held by the Maybe. If this
is Nothing returns Nothing, if this
is Just, returns the result of the combiner
method over the value
inside Just
Implementation
Maybe<K> mapJust<K>(Maybe<K> Function(T) combiner) {
return when(
nothing: () => Nothing<K>(),
just: (T data) => combiner(data),
);
}