code: public ThingGroupMetadata withRootToParentThingGroups(GroupNameAndArn... rootToParentThingGroups) {
          if (this.rootToParentThingGroups == null) {
              setRootToParentThingGroups(new java.util.ArrayList<GroupNameAndArn>(rootToParentThingGroups.length));
          }
          for (GroupNameAndArn ele : rootToParentThingGroups) {
              this.rootToParentThingGroups.add(ele);
          }
          return this;
      }
docs: <p>
  The root parent thing group.
  </p>
  <p>
  <b>NOTE:</b> This method appends the values to the existing list (if any). Use
  {@link #setRootToParentThingGroups(java.util.Collection)} or
  {@link #withRootToParentThingGroups(java.util.Collection)} if you want to override the existing values.
  </p>
  
  @param rootToParentThingGroups
  The root parent thing group.
  @return Returns a reference to this object so that method calls can be chained together.