remove(object3d) {
    if (!(object3d instanceof Object3D)) {
      throw new Error('Invalid Object3D trying to remove anchor');
    }
    const anchor = this.object3DsToAnchors_.get(object3d);
    if (!anchor) {
      return false;
    }
    this.anchorsToObject3Ds_.delete(anchor);
    this.object3DsToAnchors_.delete(object3d);
    this.vrDisplay_.removeAnchor(anchor);
    return true;
  }
Delete anchor associated to the THREE.Object3D.
@param {THREE.Object3D} object3d The ThreeJS Object3D that has an anchor
associated to it and that should be removed.
@return {boolean} A flag indicating if the removal of the anchor was
successful (true) or not (false, in case there is no anchor for the given
Object3D).