Printing outline-heading-alist in a neat way

Question

I want to print the value of outline-heading-alist but in a neater way than doing (message "%S" ounline-heading-alist) because this gives

((";;; H1" . 1) (";;; H2" . 2) (";;; H3" . 3) (";;; H4" . 4) (";;; H5" . 5) (";;; H6" . 6) (";;; H7" . 7) (";;; H8" . 8) (";;; M1" . 1) (";;; M2" . 2) (";;; M3" . 3) (";;; M4" . 4) (";;; M5" . 5) (";;; M6" . 6) (";;; M7" . 7) (";;; M8" . 8))

Here is the interactive function I have started with.

(defun message-outlhg ()
  "TODO."
  (interactive)
  (message "%s %S" "outline-heading-alist:" outline-heading-alist))