((output
  (((f.ml (1 0) (1 12))
    (2
     (label
      ((root (f.ml (page f.ml) 00000000000000000000000000000000) f.ml)
       (label foo-bar)))
     (((f.ml (1 4) (1 7)) (word foo)) ((f.ml (1 7) (1 8)) space)
      ((f.ml (1 8) (1 11)) (word Bar)))))))
 (warnings
  ( "File \"f.ml\", line 1, characters 0-3:\
   \nHeading label should not be empty.")))
