input: Write a python function to sort a list of numbers using the quick sort algorithm.
  assert quick_sort([3, 6, 8, 10, 1, 2, 1]) == [1, 1, 2, 3, 6, 8, 10]
  assert quick_sort([1, 4, 3, 9, 2]) == [1, 2, 3, 4, 9]
  assert quick_sort([10, 7, 8, 9, 1, 5]) == [1, 5, 7, 8, 9, 10]
output: def quick_sort(arr):
      if len(arr) <= 1:
          return arr
      pivot = arr[len(arr) // 2]
      left = [x for x in arr if x < pivot]
      middle = [x for x in arr if x == pivot]
      right = [x for x in arr if x > pivot]
      return quick_sort(left) + middle + quick_sort(right)