Filters the list of a user’s sites before it is populated.
Passing a non-null value to the filter will effectively short circuit get_blogs_of_user(), returning that value instead.
(null|array) An array of site objects of which the user is a member.
(int) User ID.
(bool) Whether the returned array should contain all sites, including those marked 'deleted', 'archived', or 'spam'. Default false.