code: @Override
      public ModelNode toModelNode() throws CommandFormatException {
          ModelNode node = new ModelNode();
          ModelNode groupsNode = node.get(Util.CONCURRENT_GROUPS);
          for(SingleRolloutPlanGroup group : groups) {
              groupsNode.get(group.getGroupName()).set(group.toModelNode());
          }
          return node;
      }
docs: /* (non-Javadoc)
  @see org.jboss.as.cli.operation.impl.RolloutPlanGroup#toModelNode()