input: Write a python function to find the maximum value in a list.
  assert find_max([40, 50, 11, 70, 39]) == 70
  assert find_max([1, 2, 3, 4, 5]) == 5
  assert find_max([-10, -20, -30, -5, -1]) == -1
output: def find_max(lst):
      return max(lst)