input: Write a python function to find the maximum value in a list.
  assert max_val([1, 4, 8, 10]) == 10
  assert max_val([10, 20, 5, 7, 25]) == 25
  assert max_val([-5, -1, -8, -3]) == -1
output: def max_val(lst):
      return max(lst)