input: Write a python function to get the maximum value from a list.
  assert get_max([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]) == 10
  assert get_max([10, 20, 45, 67, 84, 93]) == 93
  assert get_max([5, 7, 9, 8, 6, 4, 3]) == 9
output: def get_max(lst):
      if not lst:
          return None
      max_value = lst[0]
      for num in lst:
          if num > max_value:
              max_value = num
      return max_value