(Changed in version 2.8.0) collect has changed. The previous behavior can be reproduced with toSeq.
(bSONIterator: MonadOps[BSONElement]).filter(p)
(bSONIterator: MonadOps[BSONElement]).flatMap(f)
(bSONIterator: MonadOps[BSONElement]).map(f)
(bSONIterator: MonadOps[BSONElement]).withFilter(p)