错误TypeError：“ NoneType”类型的参数不可迭代

Question

我正在尝试使用pyautogui和pynput在Python中编写热键。 我试过运行代码，但遇到Typeerror：在似乎是执行行的地方，Nonetype是不可迭代的。 我看过其他有类似问题的问题，但是这些解决方案不能解决我的问题。 我想念什么？ 谢谢你的帮助。

from pynput import keyboard
from pynput.keyboard import Controller, Listener
import pyautogui
from pyautogui import *


# The key combination to check
COMBINATIONS = [
    pyautogui.hotkey('Cttl', 'shift', 'z')
]

# The currently active modifiers
current = set()


def execute():
    keyboard.KeyCode(char='K'), pyautogui('Ctrl', 's')
    print ("K pressed")


def on_press(key):
    if any([key in COMBO for COMBO in COMBINATIONS]):
        current.add(key)
        if any(all(k in current for k in COMBO) for COMBO in COMBINATIONS):
            execute()


def on_release(key):
    if any([key in COMBO for COMBO in COMBINATIONS]):
        current.remove(key)

with Listener(
        on_press=on_press,
        on_release=on_release) as listener:
    listener.join()