code: public Boolean isReply() {
      if (getPostId() != null && getParentId() != null) {
        return !getPostId().equals(getParentId());
      } else {
        return null;
      }
  
    }
docs: returns {@code true} if the added comment is a reply (a comment to a comment), {@code false} otherwise
  
  may be {@code null}, if it is not possible to check
  
  @return {@code true} if it is a Reply, {@code false}, may be {@code null}