docs: @Override
      void collectRangeVariables(RangeVariable[] rangeVariables, Set set) {
  
          for (int i = 0; i < nodes.length; i++) {
              if (nodes[i] != null) {
                  nodes[i].collectRangeVariables(rangeVariables, set);
              }
          }
  
          if (rangeVariable != null) {
              for (int i = 0; i < rangeVariables.length; i++) {
                  if (rangeVariables[i] == rangeVariable) {
                      set.add(rangeVariables[i]);
                  }
              }
          }
      }