code: def get_isbn13_checksum(isbn):
      
      multipliers = map(lambda x: int(x), list("13" * 6))
  
      rest = sum([i * x for i, x in zip(multipliers, isbn)]) % 10
  
      if rest == 0:
          return rest
  
      return 10 - rest
docs: Args:
          isbn (str/list): ISBN number as string or list of digits.
  
      Warning:
          Function expects that `isbn` is only 12 digits long.
  
      Returns:
          int: Last checksum digit for given `isbn`.