((output
  (((f.ml (1 0) (1 7))
    (0
     (label
      ((root (f.ml (page f.ml) 00000000000000000000000000000000) f.ml)
       (label foo)))
     (((f.ml (1 3) (1 6)) (word Foo)))))))
 (warnings
  ( "File \"f.ml\", line 1, characters 0-7:\
   \nTitle-level headings {0 ...} are only allowed in pages.")))
