docs: @Override
      public TreeNode processMerge(TreeNode node) {
  
          DefaultMutableTreeNode masterNode = (DefaultMutableTreeNode) node;
  
          // if master and slave are the same object return the
          // masterNode
          if (masterNode.equals(slaveTopNode)) {
              return masterNode;
          }
  
          // If there are not children in slaveTopNode return the
          // masterNode
          if (slaveTopNode.getChildCount() == 0) {
              return masterNode;
          }
  
          mergeNodes(masterNode, slaveTopNode);
          return masterNode;
      }