input: Write a python function to generate all permutations of a list.
  assert permutations([1, 2, 3]) == [[1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 1, 2], [3, 2, 1]]
  assert permutations([0, 1]) == [[0, 1], [1, 0]]
  assert permutations([1]) == [[1]]
output: def permutations(lst):
      if len(lst) == 0:
          return [[]]
      result = []
      for i in range(len(lst)):
          rest = lst[:i] + lst[i+1:]
          for p in permutations(rest):
              result.append([lst[i]] + p)
      return result