def purify(even):

numbers = []

for number in even:

if not (number in even):

numbers += number

return numbers

Oops, try again. Your function fails on purify([4, 5, 5, 4]). It returns [] when it should return [4, 4].

```
def purify(even):
numbers = []
for number in even:
if not (number in even):
numbers += number
return numbers
```