input: Write a function that takes an array and returns the array sorted 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([7, 4, 6, 5]) == [4, 5, 6, 7]
  assert sort_ascending([]) == []
  assert sort_ascending([1]) == [1]
  assert sort_ascending([3, 3, 3]) == [3, 3, 3]
output: def sort_ascending(array):
    array.sort()
    return array