code: def validate_headers(self):
          
          super().validate()
          self.validate_header(self.channeldir, self.channelinfo, CHANNEL_INFO_HEADER)
          self.validate_header(self.channeldir, self.contentinfo, CONTENT_INFO_HEADER)
          if self.has_exercises():
              self.validate_header(self.channeldir, self.exercisesinfo, EXERCISE_INFO_HEADER)
              self.validate_header(self.channeldir, self.questionsinfo, EXERCISE_QUESTIONS_INFO_HEADER)
docs: Check if CSV metadata files have the right format.