And just to look ahead a little bit, you could easily imagine that I might want to not just put a statement in there, what the specs are, I might want to put some constraints. Some specific things to check for, to make sure that you're calling the code right.

这不仅是抽象的概念还有规范的概念，我们再往前看看,你可以简单的想象得到，我不仅仅是想在这里加一个声明,这些规范说明中我还想加一些约束，我们要注意一些特殊的事情。

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