code: private Collection<Facet> filter(Collection<Facet> facets) {
          if (NotStopWordPredicate == null) {
              return facets;
          }
  
          return facets.stream()
                       .filter(NotStopWordPredicate)
                       .collect(Collectors.toList());
  
      }
docs: Filter stop word facets
  
  @param facets Input facets
  
  @return