Eris\Generator\FrequencyGenerator::ensureIsFrequency PHP 메소드

    private function ensureIsFrequency($frequency)
    {
        if (!is_int($frequency) || $frequency < 0) {
            throw new InvalidArgumentException('Frequency must be an integer greater or equal than 0, given: ' . var_export($frequency, true));
        }
        return $frequency;
    }