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