code: def save_cards(cards, filename=None):
      
      filename = filename or "cards-%s.txt" % (time.strftime("%Y%m%d"))
  
      with open(filename, "w") as deck_file:
          card_reprs = ["%s %s\n" % (card.value, card.suit) for card in cards]
          card_reprs[-1] = card_reprs[-1].rstrip("\n")
          for card in card_reprs:
              deck_file.write(card)
docs: Save the given cards, in plain text, to a txt file.
  
      :arg cards:
          The cards to save. Can be a ``Stack``, ``Deck``, or ``list``.
      :arg str filename:
          The filename to use for the cards file. If no filename given,
          defaults to "cards-YYYYMMDD.txt", where "YYYYMMDD" is the year, month,
          and day. For example, "cards-20140711.txt".