How can I use َ Angular ng-template as item template in vis-timeline Package?

Question

I want to create timeline view in my project (Angular 9). I use the vis-timeline package for this purpose. I don't want to create HTML manually for item template, I want to use ng-template instead, but can not set ng-template as item template.

var options = {
  editable: true,       // true or false
  template: (item, element, data) => { }         // How set ng-template?
};

Here is my Stackblitz code:

https://stackblitz.com/edit/angular-9-starter-xjykf3?file=src/app/custom-template/custom-template.component.ts

1. vis-timeline itemTemplates example (Create HTML manually)

2. vis-timeline itemTemplate document