AttributeError: 'Game' object has no attribute 'used_locations'

from cards import Card
import random


class Game():
    def __init__(self):
        self.size = 4
        self.card_options = ['Add', 'Boo', 'Cat', 'Dev', 'Egg', 'Far', 'Gum', 'Hut']
        self.columns = ['A', 'B', 'C', 'D']
        self.cards = []
        self.locations = []
        for column in self.columns:
            for num in range(1, self.size + 1):
                self.locations.append(f'{column}{num}')

    def set_cards(self):
        used_locations = []
        for word in self.card_options:
            for i in range(2):
                avaliable_locations = set(self.locations) - set(self.used_locations)
                random_location = random.choice(list(avaliable_locations))
                used_locations.append(random_location)
                card = Card(word, random_location)
                self.cards.append(card)

if __name__ == '__main__':
    game = Game()
    game.set_cards()
    for card in game.cards:
        print(card)