Custom Panel Extending HaPanelIframe?


I’m new to developing anything for Home Assistant and looking to create a custom panel that will be a slightly modified version of panel_iframe / HaPanelIframe ( frontend/ha-panel-iframe.ts at b31a9d590ef53916cc6f481efa877a57b6f756af · home-assistant/frontend · GitHub )

Is it possible to import this and use as a parent class? IE:

class CustomIFrame extends HaPanelIframe {

Ideally I’d like to keep it external and not require a custom frontend build.