Generate a random CPR number (Central Person Registry).

        :return: CPR number.

        :Example:
            0105865167

def cpr(self) -> str:
        """Generate a random CPR number (Central Person Registry).

        :return: CPR number.

        :Example:
            0105865167
        """
        day = '{:02d}'.format(self.random.randint(1, 31))
        month = '{:02d}'.format(self.random.randint(1, 12))
        year = '{:02d}'.format(self.random.randint(0, 99))
        serial_number = '{:04d}'.format(self.random.randint(0, 9999))

        cpr_nr = '{}{}{}{}'.format(day, month, year, serial_number)

        return cpr_nr