question: public final Mono < T > otherwise ( Function < ? super Throwable , ? extends Mono < ? extends T > > fallback ) { return onAssembly ( new MonoOtherwise < > ( this , fallback ) ) ; }
target:  Subscribe to a returned fallback publisher when any error occurs. <p> <img class="marble" src="https://raw.githubusercontent.com/reactor/projectreactor.io/master/src/main/static/assets/img/marble/otherwise.png" alt=""> <p>