How can I get a list of items being returned using the POST /rest/default/V1/returns endpoint?

Question

I am trying to get access to items that are being returned by customers. I am trying to access this information using the Magento /returns endpoint. The problem is that when I access this endpoint I see an attribute called "items" but it is returning None

When I look at the return via UI I can see 2 sections: The first section contains customer return information. The second section contains items that the customer is requesting to return. This is what I see in the Magento Admin UI:

However, when I try to look at the return data for the same return using the Magento returns/ API this is what I see:

Endpoint: "https://www.magento-store.com/rest/default/V1/returns/000001502"

{'increment_id': '000001502',
 'entity_id': 1502,
 'order_id': 710239,
 'order_increment_id': '1000535018',
 'store_id': 1,
 'customer_id': 163109,
 'date_requested': '2020-06-24 17:17:32',
 'customer_custom_email': None,
 'items': None,
 'status': 'pending',
 'comments': None,
 'tracks': None}

I was thinking that a list of items being returned would be found in the 'items' attribute but as you can see it is showing up as None.

At first I thought it may be an issue with the way permissions are setup but I enabled all permissions just to test and I got the same result.