input: Write a function to compute the standard deviation of a list of numbers.
  assert compute_std_dev([1, 2, 3, 4, 5]) == 1.4142135623730951
  assert compute_std_dev([10, 12, 23, 23, 16, 23, 21, 16]) == 4.898979485566356
  assert compute_std_dev([2, 4, 4, 4, 5, 5, 7, 9]) == 2.0
output: def compute_std_dev(numbers):
      if len(numbers) == 0:
          return 0
      mean = sum(numbers) / len(numbers)
      variance = sum((x - mean) ** 2 for x in numbers) / len(numbers)
      std_dev = variance ** 0.5
      return std_dev