input: Write a function to sort an array in ascending order using Python. If the given array is empty, return the 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([]) == []
output: def sort_ascending(array):
      if not array:
          return []
      array.sort()
      return array