Imports from _async module doesn't get converted to imports from _sync

Imports from the _async module seem to be unaffected:
```py
from library._async.module import AsyncFoo
```
gets converted to
```py
from library._async.module import SyncFoo
```

Expected result:

```py
from library._sync.module import SyncFoo
```

Currently working around it by exporting both the classes from a common place, but it'd be nice to have this work.