Fired when a session is initialized. This is either when:
- a new session is started, e.g. when chart.startNewSession() is called, or when the user clicks on the "start over" button on the "session expired" dialog
- or when the chart is (re-)rendered with an already active session, e.g. after a browser refresh.
holdToken parameter that gets passed into this callback is an object with the following structure:
You can listen to this event to update a timer in your host page.