Here is the document which I'm following. Under the section of Event code examples, the "product_ids" key is there.<script>
pintrk('track', 'checkout', { 
   value: 10.00, 
   order_quantity: 2, 
   currency: 'USD', 
   event_id: 'eventId0001',
   product_ids: ['1414', '1415'] }
);
</script>
<noscri...