'Set a cookie if policy says it\'s OK to do so.'

def set_cookie_if_ok(self, cookie, request):

    self._cookies_lock.acquire()
    try:
        self._policy._now = self._now = int(time.time())
        if self._policy.set_ok(cookie, request):
            self.set_cookie(cookie)
    finally:
        self._cookies_lock.release()
