Get Content Descendants

Returns a map of the descendants of a piece of content. This is similarto [Get content children](#api-content-id-child-get), except that thismethod returns child pages at all levels, rather than just the directchild pages.A piece of content has different types of descendants, depending on its type:- `page`: descendant is `page`, `comment`, `attachment`- `blogpost`: descendant is `comment`, `attachment`- `attachment`: descendant is `comment`- `comment`: ...