private function normalizeBetweenValues(array $values): ?array
    {
        if (2 !== \count($values)) {
            $this->getLogger()->notice('Invalid filter ignored', [
                'exception' => new InvalidArgumentException(sprintf('Invalid format for "[%s]", expected "<min>..<max>"', self::PARAMETER_BETWEEN)),
            ]);

            return null;
        }

        if (!is_numeric($values[0]) || !is_numeric($values[1])) {
            $this->getLogger()->notice('Invalid filter ignored', [
                'exception' => new InvalidArgumentException(sprintf('Invalid values for "[%s]" range, expected numbers', self::PARAMETER_BETWEEN)),
            ]);

            return null;
        }

        return [$values[0] + 0, $values[1] + 0]; // coerce to the right types.
    }