code: def process_files(self):
          
          config.LOGGER.info("\t*** Processing images for exercise: {}".format(self.title))
          downloaded = super(ExerciseNode, self).process_files()
          for question in self.questions:
              downloaded += question.process_question()
  
          self.process_exercise_data()
  
          config.LOGGER.info("\t*** Images for {} have been processed".format(self.title))
          return downloaded
docs: process_files: goes through question fields and replaces image strings
              Args: None
              Returns: None