extract headers from response record

[Mortimer Cladwell <mbcladwell@gmail.com>]

Hi,
I am running a local fake Urbit zod on port 8080. I want to submit an
http-request and obtain an urbauth id cookie. I run the following method:

(use-modules (web client)(web response) (srfi srfi-9)(oop goops) (ice-9
receive) (ice-9 pretty-print))

(define (urbit-http-connect)
  (let* ((uri "http://localhost:8080/~/login")
         (data (string-append "password=" "lidlut-tabwed-pillex-ridrup"))
(a (receive (response body)
  (http-request uri #:method 'POST #:body data)
     response)))
  (pretty-print a)))

==> #<<response> version: (1 . 1) code: 204 reason-phrase: "ok" headers:
((date . #<date nanosecond: 0 second: 29 minute: 49 hour: 13 day: 9 month:
8 year: 2023 zone-offset: 0>) (connection close) (server .
"urbit/vere-2.11") (set-cookie .
"urbauth-~zod=0v7.126dd.8rbvk.lga05.jvieb.287to; Path=/; Max-Age=604800"))
port: #<closed: file 7fc2a569b3f0>>

Below I substitute (pretty-print a) with various commands and show the
response:

(pretty-print  (class-of a)) ==> #<<class> <<response>> 7f721fc4c280>
(pretty-print  (record? a)) ==> #t
(pretty-print  (response? a)) ==> #f

(pretty-print  (response-headers a)) ==> In procedure response-headers:
Wrong type argument: #<<response> version: (1 . 1) code: 204 reason-phrase:
"ok" headers: ((date . #<date nanosecond: 0 second: 34 minute: 0 hour: 14
day: 9 month: 8 year: 2023 zone-offset: 0>) (connection close) (server .
"urbit/vere-2.11") (set-cookie .
"urbauth-~zod=0v5.9pm4c.pa0qd.00hao.vsq1p.h37hh; Path=/; Max-Age=604800"))
port: #<closed: file 7fbaa95eb3f0>>

So I have a record that looks like a <response> record but isn't. How do I
extract the headers from this 'response'?
How do I determine the record type?
Thanks
Mortimer