code: def get_choice_status(self):
          
          if 'choiceInfo' not in self.dto[self.name]:
              raise GPException('not a choice parameter')
  
          status = self.dto[self.name]['choiceInfo']['status']
          return status['message'], status['flag']
docs: Returns a message field, which indicates whether choices statically
          or dynamically defined, and flag indicating whether a dynamic file
          selection loading error occurred.
  
          Throws an error if this is not a choice parameter.