## Summary
This PR fixes a bug where the `Generator` wouldn't add a newline before
a type alias statement. This is because it wasn't using the `statement`
macro which takes care of the newline.
Without this fix, a code like:
```py
type X = int
type Y = str
```
The generator would produce:
```py
type X = inttype Y = str
```
## Test Plan
Add a test case.
8db147c09d