input: Write a python function to split a list into two parts at a random index.
  assert len(split_list([1, 2, 3, 4, 5, 6, 7, 8]))==2
  assert sum(split_list([1, 2, 3, 4, 5, 6, 7, 8])[0] + split_list([1, 2, 3, 4, 5, 6, 7, 8])[1]) == sum([1, 2, 3, 4, 5, 6, 7, 8])
  assert set(split_list([1, 2, 3, 4, 5, 6, 7, 8])[0] + split_list([1, 2, 3, 4, 5, 6, 7, 8])[1]) == set([1, 2, 3, 4, 5, 6, 7, 8])
output: import random
  
  def split_list(lst):
      if not lst:
          return [], []
      split_index = random.randint(0, len(lst))
      return lst[:split_index], lst[split_index:]