input: Write a function to find the maximum number in a list of integers.
  assert findMax([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]) == 10
  assert findMax([10, 20, 45, 67, 84, 93]) == 93
  assert findMax([5, 7, 9, 8, 6, 4, 3]) == 9
output: def findMax(lst):
      if not lst:
          return None
      max_num = lst[0]
      for num in lst:
          if num > max_num:
              max_num = num
      return max_num