input: Write a function to take an array as input and return the array sorted in ascending order. If the array is empty, return an empty array.
  def sort_ascending(array):
    if not array:
      return []
    array.sort()
    return array
  
  assert sort_ascending([10, 3, 9, 1, 15, 2]) == [1, 2, 3, 9, 10, 15]
  assert sort_ascending([]) == []
  assert sort_ascending([5, -2, 7, 8]) == [-2, 5, 7, 8]
  assert sort_ascending([3, 3, 1, 3]) == [1, 3, 3, 3]
  assert sort_ascending([1]) == [1]
output: def sort_ascending(array):
    if not array:
      return []
    array.sort()
    return array