input: Write a function to find the maximum element in a list.
  assert find_max([2, 4, 6, 1, 7, 12]) == 12
  assert find_max([10, 20, 30, 5]) == 30
  assert find_max([-1, -2, -3, -4]) == -1
output: def find_max(lst):
      return max(lst)