code: public static String[] add(String[] base, String... extraTags) {
          if (null == base || base.length == 0) {
              return extraTags;
          }
          if (extraTags.length == 0) {
              return base;
          }
          List<String> tags = new ArrayList<>(Arrays.asList(base));
          tags.addAll(Arrays.asList(extraTags));
          return tags.toArray(new String[tags.size()]);
      }
docs: Add extra tags to the existing set.
  
  @param base base set of tags
  @param extraTags tags which need to be added
  @return class