这时产品对象已经被转换成为了正确的类，所以您不需要自己再次的转换它。
This was already cast as the correct class of product object, so you do not need to cast it yourself.
您不需要知道它的所有内容才能有效地使用它。
You don't have to know everything about it to use it effectively.
您不需要知道它的所有内容才能有效地使用它。
You don't have to know everything about it to use it effectively.
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