其中一个是称为tag的简单字符串。

One of these is a simple string called tag.

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一个是channel类的一个实例(称为channel)。

One is an instance of the channel class (called channel).

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第一个是主目标，称为build。

The first is the main target, called build.

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第一个是主目标，称为build。

The first is the main target, called build.

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