该对象允许您访问那些要与扩展一起使用的其他服务和对象。
This object lets you access the other services and objects that you want to use with your extension.
可以从这个顶级对象访问这个提要的标题和其他信息。
The title and other information about the feed can be accessed from this top-level object.
其他所有事项，包括要访问的对象成员，都不能在消息之间进行更改，因此都纳入到模板定义中。
Everything else, including which members of the objects to access, doesn't change between messages and so goes into the template definition.
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