input: Write a function to sort an array in ascending order.
  def sort_ascending(array):
    array.sort()
    return array
  
  assert sort_ascending([10, 3, 9, 1, 15, 2])==[1, 2, 3, 9, 10, 15]
  assert sort_ascending([5, 2, 9, 1, 5, 6])==[1, 2, 5, 5, 6, 9]
  assert sort_ascending([])==[]
output: def sort_ascending(array):
    array.sort()
    return array