code: public @NotNull OptionalDouble findOptionalDouble(@NotNull SqlQuery query) {
          Optional<Double> value = findOptional(Double.class, query);
          return value.isPresent() ? OptionalDouble.of(value.get()) : OptionalDouble.empty();
      }
docs: Finds a unique result from database, converting the database row to double using default mechanisms.
  Returns empty if there are no results or if single null result is returned.
  
  @throws NonUniqueResultException if there are multiple result rows