when i add function to modules/topaz.py

```
    @moduledef.function("convert_type")
    def method_convert_type(self, space, w_obj, w_type, w_method):
        return space.convert_type(w_obj, w_type, w_method)
```

this code works, `python -mtopaz -e 'p Topaz.convert_type(1, Fixnum, "to_int")'`
but compilation breaks.