- "Toggle visiting of image files as images.
-With prefix argument ARG, turn on if positive, otherwise off.
-Returns non-nil if the new state is enabled.
+ "Toggle visiting of image files as images (Auto Image File mode).
+With a prefix argument ARG, enable Auto Image File mode if ARG is
+positive, and disable it otherwise. If called from Lisp, enable
+the mode if ARG is omitted or nil.