input: Write a python function to find the maximum element in a list.
  assert find_max([10, 9, 11, 12, 5]) == 12
  assert find_max([1, 2, 3, 4, 5]) == 5
  assert find_max([-1, -2, -3, -4, -5]) == -1
output: def find_max(lst):
      return max(lst)