code: public <T> T findUnique(@NotNull RowMapper<T> mapper, @NotNull SqlQuery query) {
          return executeQuery(mapper.unique(), query);
      }
docs: Finds a unique result from database, using given {@link RowMapper} to convert the row.
  
  @throws NonUniqueResultException if there is more then one row
  @throws EmptyResultException if there are no rows