$cssName

name of the widget the CSS of which you want to inherit for a custom widget

string $cssName;

Example

webix.protoUI({
    name:"mymultiselect",
    $cssName:"richselect",
    //other properties and methods
}, webix.ui.richselect);
 
webix.ui({ view:"mymultiselect"});

Details

By default, a custom widget inherits API of the widgets and mixins that are used for it, but not CSS.