The type of value being queried, which here is a string value

正在查询的值类型，这里是一个字符串值

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Maintain state, which here is represented by a simple string variable.

维护状态，例子中用了简单的字符串变量来代表。

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Maintain state, which here is represented by a simple string variable.

维护状态，例子中用了简单的字符串变量来代表。

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