code: function collapse() {
      this.dispatchEvent( 'collapseBegin', { target: this } );
  
      previousHeight = element.scrollHeight;
      element.style.maxHeight = '0';
      _baseTransition.applyClass( CLASSES.COLLAPSED );
  
      return this;
    }
docs: Collapses the expandable content
  @returns {ExpandableTransition} An instance.