FetcherDeferredRelSeqMany
sangria.execution.deferred.FetcherDeferredRelSeqMany
case class FetcherDeferredRelSeqMany[Ctx, RelId, T, Tmp, Id](source: Fetcher[Ctx, T, Tmp, Id], rel: Relation[T, Tmp, RelId], relIds: Seq[RelId]) extends DeferredRelSeqMany[T, RelId]