code: public static Function<? super ReactiveSeq<Long>, ? extends ReactiveSeq<Long>> filterLongs(LongPredicate b){
  
          return a->a.longs(i->i,s->s.filter(b));
      }
docs: /*
  Fluent filter operation using primitive types
  e.g.
  <pre>
  {@code
  import static cyclops.ReactiveSeq.filterInts;
  
  ReactiveSeq.ofLongs(1l,2l,3l)
  .to(filterLongs(i->i>2));
  
  //[3l]
  }
  </pre>