input: def calculate_average(numbers: List[float]) -> float:
      """Calculates the average of a list of numbers.
      >>> calculate_average([1.0, 2.0, 3.0, 4.0, 5.0])
      3.0
      >>> calculate_average([10.5, 20.3, 30.1, 40.7])
      25.4
      """
output:     total = sum(numbers)
      count = len(numbers)
      return total / count