_type "playlist" indicates multiple videos.
- There must be a key "entries", which is a list or a PagedList object, each
- element of which is a valid dictionary under this specfication.
+ There must be a key "entries", which is a list, an iterable, or a PagedList
+ object, each element of which is a valid dictionary by this specification.
Additionally, playlists can have "title" and "id" attributes with the same
semantics as videos (see above).