input: Write a function to find the smallest number in a list of numbers.
  def find_smallest_number(numbers):
      smallest = numbers[0] 
      for num in numbers:
          if num < smallest:
              smallest = num
      return smallest
  
  assert find_smallest_number([5, 4, 12, 17, 9])==4
  assert find_smallest_number([-3, 0, 15, -2])==-3
  assert find_smallest_number([10])==10
  assert find_smallest_number([7, 7, 7])==7
  assert find_smallest_number([100, 200, -4, 15])==-4
output: def find_smallest_number(numbers):
      smallest = numbers[0] 
      for num in numbers:
          if num < smallest:
              smallest = num
      return smallest