@Override
    public final <B> Maybe<B> fmap(Function<? super A, ? extends B> fn) {
        return Monad.super.<B>fmap(fn).coerce();
    }
@ Override public final < B > Maybe < B > fmap ( Function < ? super A , ? extends B > fn ) { return Monad . super . < B > fmap ( fn ) . coerce ( ) ; }
{@inheritDoc}
<p>
If the value is present, return {@link Maybe#just} <code>fn</code> applied to the value; otherwise, return
{@link Maybe#nothing}.