input: Write a function to calculate the average of a list of comma-separated numbers.
  assert calculate_average("3, 4, 5, 6, 7") == 5.0
  assert calculate_average("10, 20, 30, 40") == 25.0
  assert calculate_average("1, 2, 3, 4, 5, 6, 7, 8, 9, 10") == 5.5
output: def calculate_average(numbers: str) -> float:
      num_list = [int(num) for num in numbers.split(",")]
      return sum(num_list) / len(num_list)