code: def calculate_avg_score(res):
      
      c_star_score = 6
      avg_score = 0.0
      nb_reviews = 0
      for comment in res:
          if comment[c_star_score] > 0:
              avg_score += comment[c_star_score]
              nb_reviews += 1
      if nb_reviews == 0:
          return 0.0
      avg_score = avg_score / nb_reviews
      avg_score_unit = avg_score - math.floor(avg_score)
      if avg_score_unit < 0.25:
          avg_score = math.floor(avg_score)
      elif avg_score_unit > 0.75:
          avg_score = math.floor(avg_score) + 1
      else:
          avg_score = math.floor(avg_score) + 0.5
      if avg_score > 5:
          avg_score = 5.0
      return avg_score
docs: private function
      Calculate the avg score of reviews present in res
      :param res: tuple of tuple returned from query_retrieve_comments_or_remarks
      :return: a float of the average score rounded to the closest 0.5