@Override
 public KeyedQueryResult<LibraryBook> findAllByTitle() {
   return helper.findAllKeyedBy(
       LibraryDatabaseHelper.Field.title, LibraryDatabaseHelper.Order.ASC);
 }
 @Override
 public QueryResult<LibraryBook> findAllByAuthor() {
   return helper.findAllKeyedBy(
       LibraryDatabaseHelper.Field.a_last_name, LibraryDatabaseHelper.Order.ASC);
 }