code: function expandableClickHandler() {
    this.transition.toggleExpandable();
    this.toggleTargetState( this.ui.target );
  
    if ( this.isAccordionGroup ) {
      if ( this.activeAccordion ) {
        this.activeAccordion = false;
      } else {
        Events.trigger( 'accordionActivated', { target: this } );
        this.activeAccordion = true;
      }
    }
  }
docs: Event handler for when an expandable is clicked.