async def METHOD_NAME(
    mongo, pg: AsyncEngine, base_url: str, subtraction_id: str
) -> Optional[Subtraction]:
    document = await mongo.subtraction.find_one({"_id": subtraction_id})
    if document:
        document = await attach_computed(mongo, pg, base_url, document)
        return await apply_transforms(
            base_processor(document),
            [
                AttachUserTransform(mongo, ignore_errors=True),
                AttachUploadTransform(pg),
            ],
        )