input: Write a function to reverse a given list. The function should return the reversed list.
  assert reverse_list([1, 2, 3, 4, 5]) == [5, 4, 3, 2, 1]
  assert reverse_list([1, 2, 3, 4, 5, 6]) == [6, 5, 4, 3, 2, 1]
  assert reverse_list([]) == []
  assert reverse_list([1]) == [1]
output: def reverse_list(lst):
      return lst[::-1]