不明白这个“NameError: name 'self' is not defined”错误

我不断收到相同的错误消息：

回溯（最近一次通话）：文件“”，第 1 行，在
my_wallet.checkBalance(self) NameError: name 'self' 未定义

balance = 0
def intro():
    global balance
    balance = int(input("How much would you like to start with? No more than 200£! ")
    if balance > 200:
        print("I said less than 200£!")
        intro()
class wallet:
    def __init__(self,money,broke):
        self.broke = False
        self.money = balance
    def checkBalance(self):
        self.money = balance
        print(balance)
    def noCash(self):
        if balance <= 0:
            print("You're done! No more £££!"
        self.broke = True