code: public void removeAllChildren() {
          for (final GVRSceneObject so : headTransformObject.getChildren()) {
              final boolean notCamera = (so != leftCameraObject && so != rightCameraObject && so != centerCameraObject);
              if (notCamera) {
                  headTransformObject.removeChildObject(so);
              }
          }
      }
docs: Remove all children that have been added to the owner object of this camera rig; except the
  camera objects.