input: Write a function to sort a list in ascending order.
  assert sort_ascending([1, 3, 5, 2, 6]) == [1, 2, 3, 5, 6]
  assert sort_ascending([4, 3, 2, 1]) == [1, 2, 3, 4]
  assert sort_ascending([10, 9, 8, 7]) == [7, 8, 9, 10]
output: def sort_ascending(lst):
      return sorted(lst)