Return the identifier's elements (gs1_prefix, registration_group,
        registrant, publication, check_digit) as tuple.

def elements(self):
        """Return the identifier's elements (gs1_prefix, registration_group,
        registrant, publication, check_digit) as tuple."""
        return (self.gs1_prefix, self.registration_group, self.registrant,
                self.publication, self.check_digit)