input: Write a python function to compute the average of an array of numbers.
  assert compute_average([1, 2, 3, 4]) == 2.5
  assert compute_average([10, 20, 30, 40, 50]) == 30.0
  assert compute_average([5, 15, 25, 35, 45]) == 25.0
output: def compute_average(numbers):
      return sum(numbers) / len(numbers)