code: protected List<R> visitChildren(ParentNode<? extends N> node) {
      List<R> results = new ArrayList<>(node.numChildren());
      for (N child : node.getChildren()) {
        results.add(visit(child));
      }
      return results;
    }
docs: Helper to visit all the children of a node, in order.
  
  @param node The parent node whose children to visit.
  @return The list of return values from visiting the children.
  @see #visitChildrenAllowingConcurrentModification