code: def company_vat(self):
          
          vat_digits = []
  
          for _ in range(3):
              vat_digits.append(self.random_digit_not_null())
  
          for _ in range(6):
              vat_digits.append(self.random_digit())
  
          check_digit = company_vat_checksum(vat_digits)
  
          # in this case we must generate a tax number again, because check_digit
          # cannot be 10
          if check_digit == 10:
              return self.company_vat()
  
          vat_digits.append(check_digit)
  
          return ''.join(str(digit) for digit in vat_digits)
docs: Returns 10 character tax identification number,
          Polish: Numer identyfikacji podatkowej.
  
          https://pl.wikipedia.org/wiki/NIP