Html 如何找到站点密钥

我想找到任何站点的站点密钥以继续使用我的代码，我如何才能做到这一点

from python_anticaptcha import AnticaptchaClient, NoCaptchaTaskProxylessTask

api_key = ''

**site_key = '' #<----- How can i find out this?**

url = 'https://www.google.com/recaptcha/api2/demo'

client = AnticaptchaClient(api_key)
task = NoCaptchaTaskProxylessTask(url, site_key)
job = client.createTask(task)
job.join()
print job.get_solution_response()

从python_anticaptcha导入AnticaptchaClient，NoCaptchaTaskProxylessTask
api_键=“”
**站点密钥=“”#