input: Write a function to sort an array in ascending order.
  assert sort_array([3, 7, 1, 5])==[1, 3, 5, 7]
  assert sort_array([10, 2, 8, 6, 7, 5])==[2, 5, 6, 7, 8, 10]
  assert sort_array([9, 3, 4, 1, 2, 8, 7])==[1, 2, 3, 4, 7, 8, 9]
output: def sort_array(arr):
      return sorted(arr)