input: Write a python function to calculate the average score of a student over the course of a semester.
  assert avg_score([10, 8, 9, 6, 7]) == 8.0
  assert avg_score([100, 80, 75, 60, 90]) == 81.0
  assert avg_score([55, 65, 75, 85, 95]) == 75.0
output: def avg_score(scores):
      return sum(scores) / len(scores)