input: Write a function to find the maximum number in a list.
  assert get_max([7, 9, 5, 10, 2]) == 10
  assert get_max([-1, -5, -3, -4, -2]) == -1
  assert get_max([100, 200, 50, 300, 20]) == 300
output: def get_max(lst):
      return max(lst)