private boolean nodeExists(NodeType node) {
        return parentsOfNode.containsKey(node) && childrenOfNode.containsKey(node);
    }
Recursive search downwards through the inheritance graph to 
retrieve all who directly or indirectly inherits the given node
integration/schema-language-server/language-server/src/main/java/ai/vespa/schemals/index/InheritanceGraph.java