How to use the urlwatch.__user_agent__ function in urlwatch

def retrieve(self, job_state):
        headers = {
            'User-agent': urlwatch.__user_agent__,
        }

        proxies = {
            'http': os.getenv('HTTP_PROXY'),
            'https': os.getenv('HTTPS_PROXY'),
        }

        if job_state.etag is not None:
            headers['If-None-Match'] = job_state.etag

        if job_state.timestamp is not None:
            headers['If-Modified-Since'] = email.utils.formatdate(job_state.timestamp)

        if self.ignore_cached or job_state.tries > 0:
            headers['If-None-Match'] = None
            headers['If-Modified-Since'] = email.utils.formatdate(0)