network interfaces unavailable when firewall config queried via panorama proxy

Describe the bug

network.EthernetInterface.refreshall(FIREWALL) does not enumerate & add network interface configuration if the connection is proxied through panorama

e.g.

fw = pandevice.firewall.Firewall(panAddress,panUser,panPass)
network.EthernetInterface.refreshall(fw)

works, but

pano = pandevice.panorama.Panorama(panAddress, panUser, panPass)
fw = pano.find(fwSerial)
network.EthernetInterface.refreshall(fw)

doesn't.

Expected behavior

Config query should return the list of ethernet interfaces and add them as children to the firewall object whether the query is sent to the firewall directly or proxied to the firewall via panorama

Current behavior

interface child objects are only added if the query is submitted directly to the firewall. Proxied API returns an empty / null set.

Steps to reproduce

1. Add a firewall to panorama, configure its interfaces via template
2. Attempt to poll the firewall's config via panorama as detailed above

Start at network.EthernetInterface.refreshall and compare its direct-firewall path with the Panorama.find(fwSerial) path. Reproduce both examples from the issue, then verify that querying through Panorama returns the ethernet interface list and adds the interface objects as firewall children.