How does Python interpret this statement as True?

The following is a part of code RockPaperScissors, I can't figure out how Python, interpret

if answer in ("y", "yes", "Y", "Yes", "Of course"):
    return answer

this return as a True.

based on the code below:

def game():
    player = move()
    computer = random.randint(1, 3)
    result(player, computer)
    return play_again()

def start():
    print "Let's play a game of Rock, Paper, Scissors"
    while game():
        pass
    scores()

def play_again():
    answer = raw_input("Would you like to play again ?")
    if answer in ("y", "yes", "Y", "Yes", "Of course"):
        return answer
    else:
        print "ok that's enough for today !"