The optional objects are: language, copyright, managingEditor, webMaster, pubDate, lastBuildDate, category, generator, docs, cloud, ttl, image, rating, textInput, skipHours, and skipDays.

可选对象是：language, copyright、managingEditor, webMaster、pubDate, lastBuildDate、category, generator、docs、cloud、ttl、image、rating、textInput、skipHours 和 skipDays。

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