get_playlist_items seems not to work as desired

[nasbar79]

Hi,
first of all thank you very much for the package. I use it for different queries. I haven't called a query for a while and now it doesn't seem to work as desired.

get_playlist_items(filter = c(playlist_id = "abcdefg-hijklmnop"), part = "contentDetails", max_results = 51)

Instead of the playlist Videos I get only the count of the videos in the playlist.