question: public final Mono < T > otherwise ( Predicate < ? super Throwable > predicate , Function < ? super Throwable , ? extends Mono < ? extends T > > fallback ) { Objects . requireNonNull ( predicate , "predicate" ) ; return otherwise ( null ) ; }
target:  Subscribe to a returned fallback publisher when an error matching the given type occurs. <p> <img class="marble" src="https://raw.githubusercontent.com/reactor/projectreactor.io/master/src/main/static/assets/img/marble/otherwise.png" alt="">