(unless (assq 'notmuch-show-mode w3m-cid-retrieve-function-alist)
(push (cons 'notmuch-show-mode #'notmuch-show--cid-w3m-retrieve)
w3m-cid-retrieve-function-alist)))
(unless (assq 'notmuch-show-mode w3m-cid-retrieve-function-alist)
(push (cons 'notmuch-show-mode #'notmuch-show--cid-w3m-retrieve)
w3m-cid-retrieve-function-alist)))