input: Write a function to sort an array in ascending order.
  
  ### Function:
  def sort_ascending(array):
      array.sort()
      return array
  
  ### Test Cases:
  assert sort_ascending([10, 3, 9, 1, 15, 2]) == [1, 2, 3, 9, 10, 15]
  assert sort_ascending([5, 8, 2, 4, 1]) == [1, 2, 4, 5, 8]
  assert sort_ascending([]) == []
  assert sort_ascending([7]) == [7]
  assert sort_ascending([6, 3, 9, 3, 6]) == [3, 3, 6, 6, 9]
output: def sort_ascending(array):
      array.sort()
      return array