How to make the bot send a random photo?

Question

Python

Hello, I need to make a bot that will send a random photo when a person writes some text.

def init(update,context):
    if "как дела" in message.text.lower():
    directory = "/isxodniki"
    random_image = random.choice(os.listdir(directory))
    bot.send_photo(update.message.chat_id, photo=open(directory + random_image,'rb'))

It seems to have done everything right, but it does not work.
Help)