code: def identity_card_number(self):
          
          identity = []
  
          for _ in range(3):
              identity.append(self.random_letter().upper())
  
          # it will be overwritten by a checksum
          identity.append(0)
  
          for _ in range(5):
              identity.append(self.random_digit())
  
          identity[3] = checksum_identity_card_number(identity)
  
          return ''.join(str(character) for character in identity)
docs: Returns 9 character Polish Identity Card Number,
          Polish: Numer Dowodu Osobistego.
  
          The card number consists of 3 letters followed by 6 digits (for example, ABA300000),
          of which the first digit (at position 3) is the check digit.
  
          https://en.wikipedia.org/wiki/Polish_identity_card