code: def _verify_assumptions(self):
          
          text = self.annotation
          keys = text.keys()
  
          if '$MODE' not in text or text['$MODE'] != 'L':
              raise ParserFeatureNotImplementedError(u'Mode not implemented')
  
          if '$P0B' in keys:
              raise ParserFeatureNotImplementedError(u'Not expecting a parameter starting at 0')
  
          if text['$BYTEORD'] not in ['1,2,3,4', '4,3,2,1', '1,2', '2,1']:
              raise ParserFeatureNotImplementedError(u'$BYTEORD {} '
                                                     u'not implemented'.format(text['$BYTEORD']))
docs: Verify that all assumptions made by the parser hold.