[OneSignal Plugin] How to add headings?

Hi everyone. How to add headings? I want to send push notifications with heading (title) via the plugin. Right now I was only able to send the content only without the heading (title).

Anyone can offer help?

I modified OneSignal plugin myself to add heading.

But nowadays, since OneSignal plugin was so far from my expectations, I had switched to Firebase Cloud Message plugin for push notification.