new_contents: def checkio(data):
      total = 0
      for i, d in enumerate(c for c in reversed(data) if c.isalnum()):
          e = ord(d) - 48
          total += [sum(divmod(e*2, 10)), e][i%2]
      final = [0, 10 - total % 10][bool(total % 10)]
      return [str(final), total]
  
subject: Create check-digit.py