code: SerialFieldTag[] serialFieldTags() {
          ListBuffer<SerialFieldTag> found = new ListBuffer<>();
          for (Tag next : tagList) {
              if (next instanceof SerialFieldTag) {
                  found.append((SerialFieldTag)next);
              }
          }
          return found.toArray(new SerialFieldTag[found.length()]);
      }
docs: Return serialField tags in this comment.