public static function individualIdentificationNumber(\DateTime $birthDate = null)
{
if (!$birthDate) {
$birthDate = \Faker\Provider\DateTime::dateTimeBetween();
}
$dateAsString = $birthDate->format('ymd');
$genderAndCenturyId = (string) static::numberBetween(1, 6);
$randomDigits = (string) static::numerify('#####');
return $dateAsString . $genderAndCenturyId . $randomDigits;
}