try {
        return super.retainAll(checkNotNull(c));
      } catch (UnsupportedOperationException e) {
        // if the iterators don't support remove
        Set<@Nullable Object> keys = Sets.newHashSetWithExpectedSize(c.size());
        for (Object o : c) {
          /*
           * `o instanceof Entry` is guaranteed by `contains`, but we check it here to satisfy our
           * nullness checker.
           */

      try {
        return super.retainAll(checkNotNull(c));
      } catch (UnsupportedOperationException e) {
        // if the iterators don't support remove
        Set<@Nullable Object> keys = Sets.newHashSetWithExpectedSize(c.size());
        for (Object o : c) {
          /*
           * `o instanceof Entry` is guaranteed by `contains`, but we check it here to satisfy our
           * nullness checker.
           */