update( element, out ) {
		/* eslint-enable no-unused-vars */

		if ( element.parent && element.parent.isUI ) {

			this._value = element.parent;
			// this.position.z = this.getOffset();

		} else {

			this._value = null;

		}

		// @TODO : parentElement
		// // set elements as root
		// if ( element.isBlock && !this._value ) {
		//
		// 	ThreeMeshUI.addRoot( element );
		// 	element.pseudoClassList.add('root');
		//
		// } else {
		//
		// 	ThreeMeshUI.removeRoot( element );
		// 	element.pseudoClassList.remove('root');
		//
		// }


	}
Update when :
		- element has been added
		- element has been removed

@param element
@param out