- [x] `DBIO.unit: DBIO[Unit]` - [x] `DBIO.traverse[A, B, C[x] <: Iterable[x]](C[A])(A => DBIO[B]): DBIO[C[B]]` - [ ] `DBIO.defer[A](=>A): DBIO[A]` - [x] `[A] DBIO[A]#void: DBIO[Unit]` (or another name)