input: 
  from typing import List
  
  def max_num(list: List[int]) -> int:
      """ Finds the maximum number in a given list of integers.
      >>> max_num([9, 2, 5, 6, 4, 1])
      9
      >>> max_num([-1, -3, -5, -2, -4])
      -1
      """
  
output:     max_value = list[0]
      for num in list:
          if num > max_value:
              max_value = num
      return max_value