docs: public void setBookType(final BookType bookType) {
          if (bookType == null && this.bookType == null) {
              return;
          } else if (bookType == null) {
              removeChild(this.bookType);
              this.bookType = null;
          } else if (this.bookType == null) {
              this.bookType = new KeyValueNode<BookType>(CommonConstants.CS_BOOK_TYPE_TITLE, bookType);
              appendChild(this.bookType, false);
          } else {
              this.bookType.setValue(bookType);
          }
      }