input: Write a python function to calculate the average rating from a list of tuples, where each tuple contains two ratings.
  assert avg_rating([(1, 2), (3, 4), (5, 6)]) == 3.5
  assert avg_rating([(4, 4), (4, 4), (4, 4)]) == 4.0
  assert avg_rating([(2, 3), (1, 5), (4, 6)]) == 3.5
output: def avg_rating(ratings):
      total_sum = sum(sum(pair) for pair in ratings)
      total_count = len(ratings) * 2
      return total_sum / total_count