{"ast_node_type":"other","tokens":[{"end":98,"kind":"keyword","start":0,"text":"//"}]}
        // Instantiate any missing rows up to and including row `row` with an empty `DenseBitSet`.
    fn ensure_row(&mut self, row: R) -> &mut DenseBitSet<C> {
        // Then replace row `row` with a full `DenseBitSet` if necessary.