Comment

Lukáš

Hello guys, the ordered variant can be even faster, if you change the condition:

```
    seen = set()
    return [x for x in seq if not (x in seen or seen.add(x))]
```

and another quite important optimization is to avoid __getattr__ call by storing the actual used function:

```
    seen = set()
    seen_add = seen.add
    return [x for x in seq if not (x in seen or seen_add(x))]
```