def process_files(self):
        """ process_files: goes through question fields and replaces image strings
            Args: None
            Returns: None
        """
        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
process_files: goes through question fields and replaces image strings
            Args: None
            Returns: None