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([1, 2, 3, 4, 5])==1
  assert find_smallest_number([-1, -5, -3, -2, -4])==-5
  assert find_smallest_number([10])==10
  assert find_smallest_number([3, 2, 2, 3, 2])==2
output: def find_smallest_number(numbers):
      smallest = numbers[0] 
      for num in numbers:
          if num < smallest:
              smallest = num
      return smallest