input: Write a function to find the minimum value in a list of numbers.
  assert find_min([3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5]) == 1
  assert find_min([10, 20, 5, 7, 8, 3, 6]) == 3
  assert find_min([-1, -5, -3, -4, -2]) == -5
output: def find_min(numbers):
      return min(numbers)