I'm trying to implement quicksort in python. Here is my code:

```
def quicksort(numbers):
    less = []
    is_pivot = []
    larger = []

    if len(numbers) > 1:
        pivot = numbers[0]
        for x in numbers:
            if x < pivot:
                less.append(x)
            elif x == pivot:
                is_pivot.append(x)
            else:
                larger.append(x)
        sorted_list = quicksort(less) + is_pivot + quicksort(larger)
        print(sorted_list)
    else:
        print(numbers)

```

This gives me the following error message:

```
  File "sortingalgorithms.py", line 101, in <module>
quicksort(numbers)
File "sortingalgorithms.py", line 66, in quicksort
sorted_list = quicksort(less) + is_pivot + quicksort(larger)
File "sortingalgorithms.py", line 66, in quicksort
sorted_list = quicksort(less) + is_pivot + quicksort(larger)
TypeError: unsupported operand type(s) for +: 'NoneType' and 'list'

```

When I try to print the lists without concatenating them I get the following output for a list with the numbers 3,2,1

```
[1.0]
[]
[None, [2.0], None]
[]
[None, [3.0], None]

```

Where are the nonetype elements coming from, and how can I solve my issue? Thanks