Accessing anvil.server.request.headers from a @anvil.server.callable function?

Anvil Q&A
1

What I’m trying to do:
Is it possible to access the http request header from a @anvil.server.callable function?
I know this is possible from an @anvil.server.http_endpoint(…) function, but the convenience and extras of anvil.server.callable functions are nice.

As for why I’d like to do it, I’ve a proxy in before the server that adds a few interesting fields to the header.

Code Sample:

@anvil.server.callable
def return_header():
  return "You requested user header " + str(anvil.server.request.headers)

Clone link:
https://anvil.works/build#clone:4VBYECDWW2CHEXSJ=SSV46TDXCCJU2P2HGZ43EJ7N