((output
  (((f.ml (1 0) (1 7))
    (1
     (label
      ((root (f.ml (page f.ml) 00000000000000000000000000000000) f.ml)
       (label foo)))
     (((f.ml (1 3) (1 6)) (word Foo)))))
   ((f.ml (2 0) (2 7))
    (1
     (label
      ((root (f.ml (page f.ml) 00000000000000000000000000000000) f.ml)
       (label bar)))
     (((f.ml (2 3) (2 6)) (word Bar)))))))
 (warnings
  ( "File \"f.ml\", line 2, characters 0-7:\
   \n'{1': heading level should be lower than top heading level '1'.")))
