input: def find_smallest_number(numbers: List[int]) -> int:
      """Find the smallest number in a given list of integers.
      >>> find_smallest_number([5, 4, 12, 17, 9])
      4
      >>> find_smallest_number([10, 2, 3, 5, 1])
      1
      """
output:     if not numbers:
          raise ValueError("The list is empty")
      smallest = numbers[0]
      for num in numbers:
          if num < smallest:
              smallest = num
      return smallest