Layout with header

I created a layout element that behaves like an accordion item (but as it is a single element, I can’t create the accordion parent). It works (the panel is collapsed and expanded when the user clicks on the header), but I need to execute some business logic as well, and I can’t find which event I can tap into. Can you point me in the right direction please?

webix.ui
({
	cols: [
	    {
		view: 'sidebar',
		id: 'sidebar',
		width: 150,
		data: data
	    },
	    {
		id: 'selector',
		header: ' Panel',
		width: 200,
		body: { template: '<div id="selector"/>' }
	    }
            ]

})

Please ignore, already found it. Webix created an implicit accordion parent object anyway. Just had to give it a an ID and use its ‘onAfterCollapse’ and ‘onAfterExpand’ events