remove all my added face text properties?

[Samuel Wales]

i set face properties in a roughly as follows:

(defun highlight-1 (extent)
             (let ((p (point)))
               ;; fixme what do we do to =remove= all of these
               ;; added face properties in the buffer?  we need
               ;; to do that when re-running this function to not
               ;; keep the old stuff around.
               ;;
               ;; get-text-property but we need to get all?
               ;; set-text-properties start end face?
               (add-face-text-property p (+ extent p) '(:inverse-video t))))

what does one do to keep all the text properties, including face text
properties, in the buffer, as they were before i first highlighted
anyghing, while at the same time removing the face properties i added?
 thank you.

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