docs: public final static <T> Stream<String> flatMapURL(final Stream<T> stream, final Function<? super T, URL> fn) {
          return stream.flatMap(fn.andThen(url -> ExceptionSoftener.softenSupplier(() -> {
              final BufferedReader in = new BufferedReader(
                                                           new InputStreamReader(
                                                                                 url.openStream()));
  
              return in.lines();
          })
                                                                   .get()));
  
      }