func (it *Iterator) Seek(bs []byte) {
	itm := it.snap.db.newItem(bs, false)
	it.iter.Seek(unsafe.Pointer(itm))
	it.skipUnwanted()
}
func (it *Iterator) Seek(bs []byte) {
	itm := it.snap.db.newItem(bs, false)
	it.iter.Seek(unsafe.Pointer(itm))
	it.skipUnwanted()
}
// Seek to a specified key or the next bigger one if an item with key does not
// exist.