timeline add an event using javascript

I have a task list and i want to add an event to the timeline with callout format without the user action.

So after looking for, using the javascript funciont found in sp.ui.timeline.js:

 AddItemsToTimeline([{ 'id': itemID }], listId, 'Timeline');

i was able to add the list items to the timeline but i need to add them as a callout, so i suspect has to been added with the parameter fmt = 2 instead of the default value fmt = 0.

I tried using:

AddItemsToTimeline([{ 'id': itemID,`fmt':2 }], listId, 'Timeline');

but just don't work.

please some help with this.

Thank you in advance.