How to use the rlcard.games.doudizhu.judger.cards2str function in rlcard

def deal_cards(self, players):
        ''' Deal cards to players

        Args:
            players (list): list of DoudizhuPlayer objects
        '''
        hand_num = (len(self.deck) - 3) // len(players)
        for index, player in enumerate(players):
            current_hand = self.deck[index*hand_num:(index+1)*hand_num]
            current_hand.sort(key=functools.cmp_to_key(doudizhu_sort_card))
            player.set_current_hand(current_hand)
            player.initial_hand = cards2str(player.current_hand)

def initiate(self, players):
        ''' Call dealer to deal cards and bid landlord.

        Args:
            players (list): list of DoudizhuPlayer objects
        '''
        landlord_id = self.dealer.determine_role(players)
        seen_cards = self.dealer.deck[-3:]
        seen_cards.sort(key=functools.cmp_to_key(doudizhu_sort_card))
        self.seen_cards = cards2str(seen_cards)
        self.landlord_id = landlord_id
        self.current_player = landlord_id
        self.public = {'deck': self.deck_str, 'seen_cards': self.seen_cards,
                       'landlord': self.landlord_id, 'trace': self.trace,
                       'played_cards': self.played_cards}

## determine 'landlord'
        #max_score = get_landlord_score(
        #    cards2str(self.landlord.current_hand))
        #for player in players[1:]:
        #    player.role = 'peasant'
        #    score = get_landlord_score(
        #        cards2str(player.current_hand))
        #    if score > max_score:
        #        max_score = score
        #        self.landlord = player
        #self.landlord.role = 'landlord'

        # give the 'landlord' the  three cards
        self.landlord.current_hand.extend(self.deck[-3:])
        self.landlord.current_hand.sort(key=functools.cmp_to_key(doudizhu_sort_card))
        self.landlord.initial_hand = cards2str(self.landlord.current_hand)
        return self.landlord.player_id

def _get_others_current_hand(self, player):
        player_up = self.players[get_upstream_player_id(player, self.players)]
        player_down = self.players[get_downstream_player_id(
            player, self.players)]
        others_hand = merge(player_up.current_hand, player_down.current_hand, key=functools.cmp_to_key(doudizhu_sort_card))
        return cards2str(others_hand)

def __init__(self):
        self.trace = []
        self.played_cards = []

        self.greater_player = None
        self.dealer = Dealer()
        self.deck_str = cards2str(self.dealer.deck)