input: Write a python function to generate grade based on points.
  assert generate_grade(95) == "A"
  assert generate_grade(85) == "B"
  assert generate_grade(75) == "C"
  assert generate_grade(65) == "D"
  assert generate_grade(55) == "F"
output: def generate_grade(points):
      if points >= 90:
          return "A"
      elif points >= 80:
          return "B"
      elif points >= 70:
          return "C"
      elif points >= 60:
          return "D"
      else:
          return "F"