Custom combo control not working

i m trying to create a custom combo control using webix.protoUI but getting some exception below is my snippet

https://webix.com/snippet/09e18f26

https://docs.webix.com/desktop__custom_component.html
this chapter describes creating custom components

@intregal i have follow this documentation but could not figure out.please check my snippet

a possible solution https://webix.com/snippet/d20ef537

@intregal thanks alot