docs: public boolean addChildObject(GVRSceneObject child) {
          if (child.mParent == this) {
              return false;
          }
          if (child.mParent != null) {
              throw new UnsupportedOperationException("GVRSceneObject cannot have multiple parents");
          }
          mChildren.add(child);
          child.mParent = this;
          NativeSceneObject.addChildObject(getNative(), child.getNative());
          child.onNewParentObject(this);
          return true;
      }