If argument sbmlf is an object of class character,the
  function returns TRUE, if no infos, warnings, errors or fatals
  have been found. Otherwise a the value returned is a list.
infos Infos
  warnings Warnings
  errors Errors
  fatals Fatals
  Each entry of one of these lists is again a list containing the message id,
  line and column number of the SBML file generating the message and the
  corresponding message text.  If argument sbmlf is an object of class '>sbmlPtr,
  the function returns the number of errors found in the SBML document.