code: private void insertNodeIntoIndex(QueryNode queryNode, TreeNode treeNode) {
          nodeIndex.put(queryNode, treeNode);
          if (queryNode instanceof TrueNode){
             trueNodes.add((TrueNode) queryNode);
          }
          else if (queryNode instanceof IntensionalDataNode){
              intensionalNodes.add((IntensionalDataNode) queryNode);
          }
          updateVersionNumber();
      }
docs: Low-low-level