filter IN is not working
You also contacted me via my personal site. Then opened an issue on GH. Please in the future use stackoverflow for basic questions like this.

Works fine, by the way:

```python
from peewee import *

db = SqliteDatabase(':memory:')

class Reg(Model):
    key = TextField()
    class Meta:
        database = db

db.create_tables([Reg])

for i in range(10):
    Reg.create(key='k%s' % i)


query = Reg.select().where(Reg.key.in_(['k1', 'k3', 'k5']))
for row in query:
    print(row.key)
```

Output:

```
k1
k3
k5
```

hello,
i try to use filter IN in peewee. but the generated code is not right
for example i want to select * from item where itemid in (abc, def)
but the peewee is create without "()"

so the peewee will create select * from item where itemid in abd, def
it will raised the error in mysql.

could you help me about this?