private void recordNodeInfoPresence(final K nodeKey,
                                        final ExplorerNode node) {

        final ExplorerNode parentNode = getParent(nodeKey);
        final K parentKey = getNodeKey(parentNode);
        final boolean wasAdded = parentKeyToChildNodesWithInfoMap.computeIfAbsent(parentKey, k -> new HashSet<>())
                .add(node);

        // Another descendant of parentNode may have already marked it as having child node info,
        // in which case nothing to do
        if (wasAdded && parentKey != null) {
            // Recurse up the chain of ancestors till we hit one with no parent
            recordNodeInfoPresence(parentKey, parentNode);
        }
    }
Record a child node having node info (or one of its descendants having node info.
stroom-explorer/stroom-explorer-impl/src/main/java/stroom/explorer/impl/AbstractTreeModel.java