docs: static List<String> filter(List<String> tokens) {
          List<String> result = new ArrayList<>();
          Set<String> noise = noiseWords();
          for (String token : tokens) {
              if (S.blank(token)) {
                  continue;
              }
              token = token.trim().toLowerCase();
              if (!noise.contains(token)) {
                  result.add(token);
              }
          }
          return result;
      }