我正在創建一個以登錄功能開始的游戲用戶可以“登錄 (A) 或創建帳戶(B)”我的問題是，如果用戶使用不存在的用戶名登錄，我會收到 KeyError：“（無論他們輸入什么用戶名）”預期結果： 如果發生這種情況，我希望代碼輸出“用戶不存在”?？梢允褂么舜a重現該問題，然后輸入“A”登錄并輸入不存在的隨機用戶名。users = {} # Currently empty list called Users. Stores all log insglobal statusstatus = ""def LogIn():#Function is called Log In. Can be called at any time.    status = input("Log in (A) or Create an account(B) - Enter 'A' or 'B' ")   # asks for log in information    status = status.upper()    if status == "A":        oldUser() #Already has an account    elif status == "B":        newUser() #Would like to make a new account        return status #Moves on to the function named statusdef newUser(): # Creating an account.    CreateUsername = input("Create username: ") #Enter a what your username is    if CreateUsername in users: # check if login name exists in the list        print ("\n Username already exists!\n")    else:        createPassw = input("Create password: ")        users[CreateUsername] = createPassw # add login and password        print("\nUser created!\n")     def oldUser():    username = input("Enter username: ")    passw = input("Enter password: ")    # check if user exists and login matches password    if passw == users[username]:      print ("Login successful!\n")      print('Game begins')    else:        print ("\nUser doesn't exist or wrong password!\n")while status != "q":                status = LogIn()額外信息：有關登錄功能如何工作的更多背景信息。