input: Write a function to sort a list of items in descending order. The function should modify the original list and return the sorted list.
  assert sort_descending([3, 7, 5, 8, 10])==[10, 8, 7, 5, 3]
  assert sort_descending([1])==[1]
  assert sort_descending([5, 4, 3, 2, 1])==[5, 4, 3, 2, 1]
  assert sort_descending([])==[]
output: def sort_descending(lst):
      lst.sort(reverse=True)
      return lst