Creating a drag and drop with rangy

Question

When I inspect my code it has the draggable attribute but the onDragStart is missing in the browser.

 rangy.createClassApplier(foo, {
        normalize: true,
        elementTagName: ‘mark’,
        elementProperties: {
          draggable: 'true',
          onDragStart: drag(event),
        },
    elementAttributes: {
     id: `drag${id}`,
    }
  }

On inspection this is what I see:

<mark id="drag2" draggable='true'>
here is some more
</mark>

what am I missing?