input: Write a python function to perform a custom sort on a list.
  assert custom_sort([3, 2, 1, 4]) == [1, 2, 3, 4]
  assert custom_sort([10, 5, 3, 8]) == [3, 5, 8, 10]
  assert custom_sort([1, 1, 1, 1]) == [1, 1, 1, 1]
output: def custom_sort(lst):
      return sorted(lst)