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([4, 2, 7, 1, 3])==[1, 2, 3, 4, 7]
  assert sort_ascending([])==[]
  assert sort_ascending([5])==[5]
  assert sort_ascending([9, 8, 7, 6, 5])==[5, 6, 7, 8, 9]
output: def sort_ascending(array):
    array.sort()
    return array