input: Write a python function to split a list into two halves.
  assert split_list([1, 2, 3, 4, 5, 6]) == ([1, 2, 3], [4, 5, 6])
  assert split_list(['a', 'b', 'c', 'd']) == (['a', 'b'], ['c', 'd'])
  assert split_list([10, 20, 30, 40, 50, 60, 70, 80]) == ([10, 20, 30, 40], [50, 60, 70, 80])
output: def split_list(lst):
      mid = len(lst) // 2
      return lst[:mid], lst[mid:]