Your goal in this kata is to implement a difference function, which subtracts one list from another and returns the result.
It should remove all values from list `a`, which are present in list `b`.
```python
array_diff([1,2],[1]) == [2]
```
If a value is present in `b`, all of its occurrences must be removed from the other:
```python
array_diff([1,2,2,2,3],[2]) == [1,3]
```
~~~ if:c
NOTE: In C, assign return array length to pointer *z
~~~
def array_diff(a, b):
    return [x for x in a if x not in b]
def array_diff(a, b):
    return [x for x in a if x not in b]