在Scala 中，方括号表示参数化的类；在这里，参数是ID的类型和实际模型类的类型。

The square brackets denote a parameterized class in Scala, and in this case, it takes the type of the ID and the type of the actual model class.

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在XMLEXISTS中表示谓词时，请确保使用了方括号，例如 $a/author[phone=4084511234]，而不是 $a/author/phone=4084511234。

When you express predicates in XMLEXISTS, make sure that you use square brackets such as in $a/author[phone=4084511234] rather than $a/author/phone=4084511234.

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在XMLEXISTS中表示谓词时，请确保使用了方括号，例如 $a/author[phone=4084511234]，而不是 $a/author/phone=4084511234。

When you express predicates in XMLEXISTS, make sure that you use square brackets such as in $a/author[phone=4084511234] rather than $a/author/phone=4084511234.

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