code: @Override
      public SyndCategory remove(final int index) {
          final DCSubject subject = subjects.remove(index);
          if (subject != null) {
              return new SyndCategoryImpl(subject);
          } else {
              return null;
          }
      }
docs: Removes a category element from a specific position.
  <p>
  
  @param index position to remove the category from.
  @return the SyndCategoryImpl being removed from position index, <b>null</b> if none.