input: Write a python function to find the maximum number in a list.
  ```python
  def find_max_number(lst):
      max_num = -float('inf')
      for num in lst:
          if num > max_num:
              max_num = num
      return max_num
  
  assert find_max_number([9, 2, 6, 3, -5, 5, 7]) == 9
  assert find_max_number([1, 2, 3, 4, 5]) == 5
  assert find_max_number([-1, -2, -3, -4, -5]) == -1
output: def find_max_number(lst):
      max_num = -float('inf')
      for num in lst:
          if num > max_num:
              max_num = num
      return max_num
  
  assert find_max_number([9, 2, 6, 3, -5, 5, 7]) == 9
  assert find_max_number([1, 2, 3, 4, 5]) == 5
  assert find_max_number([-1, -2, -3, -4, -5]) == -1