* the function is not invoked). Example usage:
   *
   * <pre>{@code
   * ListenableFuture<QueryResult> queryFuture = ...;
   * ListenableFuture<List<Row>> rowsFuture =
   *     transform(queryFuture, QueryResult::getRows, executor);
   * }</pre>
   *
   * <p>When selecting an executor, note that {@code directExecutor} is dangerous in some cases. See
   * the warnings the {@link MoreExecutors#directExecutor} documentation.
   *

   * the function is not invoked). Example usage:
   *
   * <pre>{@code
   * ListenableFuture<QueryResult> queryFuture = ...;
   * ListenableFuture<List<Row>> rowsFuture =
   *     transform(queryFuture, QueryResult::getRows, executor);
   * }</pre>
   *
   * <p>When selecting an executor, note that {@code directExecutor} is dangerous in some cases. See
   * the warnings the {@link MoreExecutors#directExecutor} documentation.
   *

        protected Activation.Builder transformActivation_Os(
                Supplier<? extends Activation.Builder> creator, Activation.Builder builder, Activation target) {
            stk.push(nextFrame("os", Activation::getOs));
            try {
                return super.transformActivation_Os(creator, builder, target);
            } finally {
                stk.pop();
            }
        }

        @Override