public FluxMap(Publisher<? extends T> source,Function<? super T,? extends R> mapper){
  super(source);
  this.mapper=Objects.requireNonNull(mapper,"mapper");
}

public FluxMap ( Publisher < ? extends T > source , Function < ? super T , ? extends R > mapper ) { super ( source ) ; this . mapper = Objects . requireNonNull ( mapper , "mapper" ) ; }
constructs a fluxmap instance with the given source and mapper .
