input: Write a function to return the maximum number in a list.
  assert find_max([1, 15, 20, 6]) == 20
  assert find_max([5, -2, 10, 8, 3]) == 10
  assert find_max([0, 0, 0, 0]) == 0
  assert find_max([-3, -1, -4, -2]) == -1
  assert find_max([])
  
  Thrown an exception for empty list
output: def find_max(lst):
      if not lst:
          raise ValueError("Thrown an exception for empty list")
      return max(lst)