N + 1 round trip problem

Does this library handle nested models (joins) in a single query from the server to the DB?
For example

```
user {
id
posts {
id
}
}
```

The issue names no files, tests, or entry points. Start by tracing how nested GraphQL fields are resolved into SQLAlchemy queries, then confirm the expected query count and behavior for the User and posts example. Done means the intended N+1 behavior is clearly specified and verified, or the requested support is implemented with coverage.

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