input: Write a function to find the smallest number in a list of numbers.
  assert find_smallest_number([5, 4, 12, 17, 9])==4
  assert find_smallest_number([10, 8, 15, 7])==7
  assert find_smallest_number([22, 22, 22, 22])==22
  assert find_smallest_number([-5, -10, 0, -3])==-10
  assert find_smallest_number([1])==1
output: def find_smallest_number(numbers):
      return min(numbers)