为什么需要非线性？ 想象一下，如果网络里每一层都是线性的（比如 y=Wx+b），无论堆叠多少层，最终网络都只是一条线性映射。深度堆叠就没有意义了，网络的表达能力非常有限。
if urlparse(full_url).netloc == urlparse(self.base_url).netloc:
，这一点在服务器推荐中也有详细论述
Олег Давыдов (Редактор отдела «Интернет и СМИ»)
（三）明知住宿人员利用旅馆实施犯罪活动，不向公安机关报告的。
Again, the answer to this question varies from company to company. And again, testing is the way to find out what works best. Typically, weekends and mornings seem to be times when multiple emails are opened, but since your audience may have different habits, it's best to experiment and then use your data to decide.