docs: private void buildCallHierarchy() {
                  
          final ExecutionNodeUsage rootUsage = new ExecutionNodeUsage(this.rootNode);
          
          callerHierarchy.put(rootUsage, null); // nothing calls this
          
          for (final FeatureNode feature : this.rootNode.getChildren()){
              
              addToCallHierarchy(feature);
              
              for (final ScenarioNode scenario : feature.getChildren()){
  
                  addToCallHierarchy(scenario);
  
                  processChildrenForCallHierarchy(scenario.getChildren());
              }
          }
      }