docs: def ssn(self):
          """
          Returns 11 character Polish national identity code (Public Electronic Census System,
          Polish: Powszechny Elektroniczny System Ewidencji Ludności - PESEL).
  
          It has the form YYMMDDZZZXQ, where YYMMDD is the date of birth (with century
          encoded in month field), ZZZ is the personal identification number, X denotes sex
          (even for females, odd for males) and Q is a parity number.
  
          https://en.wikipedia.org/wiki/National_identification_number#Poland
          """
          birth_date = self.generator.date_time()
  
          year_without_century = int(birth_date.strftime('%y'))
          month = calculate_month(birth_date)
          day = int(birth_date.strftime('%d'))
  
          pesel_digits = [
              int(year_without_century / 10),
              year_without_century % 10,
              int(month / 10),
              month % 10,
              int(day / 10), day % 10,
          ]
  
          for _ in range(4):
              pesel_digits.append(self.random_digit())
  
          pesel_digits.append(checksum(pesel_digits))
  
          return ''.join(str(digit) for digit in pesel_digits)